Report submitted to the Sustainability Indicators – Malta Observatory
Michelle Borg
July 20001
1

Economic Activities and Sustainability
1.1 This is a report commissioned by the Sustainability Indicators - Malta
Observatory within the Islands and Small States Institute, Valletta. The objective of the report is to focus on sustainability indicators applicable to economic activities in Malta.
The Meaning of Sustainability
1.2 The original definition of sustainable development is encapsulated in the
Brundtland Report of 1987 by the World Commission on Environment and
Development, which defines it as
‘development which meets the needs of the present without compromising the ability of futu re generations to meet their own needs.’
1.3 Several attempts have been made to redefine this term to the extent that it was wrongly being used interchangeably with terms such as ‘sustainable growth’ and
‘sustainable use’. The strategy for sustainable development proposed and published in partnership by the IUCN, UNEP and WWF (1991) gives clear definitions to explain and clearly distinguish the conceptual difference between these terms. This report adopts the same definitions, which are reproduced below.
1.4 The term ‘sustainable use’ is only applicable to renewable resources whereas
‘Sustainable growth’ is seen as a contradictory term since physical growth is finite.
Sustainable development
Sustainable economy
Improving the quality of life while living within the carrying capacity of supporting ecosystems
The product of sustainable development, it maintains the natural resource base and can continue to develop by adapting, and through improvement in knowledge, organisation, technical efficiency and wisdom.
Source: IUCN/UNEP/WWF 1991
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Economic Activities and Sustainability
Economic Activities and Sustainability
1.5 The improvement and maintenance of the quality of human life are intertwined with development as it provides the mechanism that transforms the natural resources into the basic infrastructure requirements ancillary to urban and rural development. Natural resources have been differentiated into renewable and non-renewable resources depending on their capacity to regenerate within a short period of time relative to a human lifespan. However even renewable resources may be degraded or depleted as a result of an activity or event that hinders its renewal cycle. Pollution is one primary source that affects resources.
Pollution incorporates any physical, chemical or biological change that adversely affects the health, survival or activities of living organisms or that alters the environment in undesirable ways . Pollution arising from human activity is controllable, unlike that induced from natural phenomena such as volcanic eruptions. This implies that action is possible to reduce, control and mitigate its impacts if not totally eliminate them.
1.6 Pearce et al (1997) recognise this inter-relationship between development and the environment and see economic development is broader in concept than economic growth, which in itself relates to increases in a defined quantity, real
GNP per capita. Broader values such as quality of life are incorporated with economic development.
It is within these concepts that the report tries to identify ways to measure the sustainability of economic activities within the Maltese Islands.
2.1 A review of the current sustainability indicators that have been identified by the
OECD, MAP/Blue Plan, EU and UN has been undertaken. Although each organisation has identified a number of indicators relating to economic activities, not all have been clearly developed. Each organisation worked on the same approach to establish indicators, mainly the State-Pressure-Response Model, which looks at establishing indicators that can highlight changes with respect to the environmental resource base, the sources of such changes and any actions that have been undertaken to overcome or mitigate impacts emanating from these changes. The Pressure Indicators are sometimes referred to as Driving
Force indicators.
2.2 Most of the indicators identified by the separate institutions are very similar, with the OECD and the UN Commission for Sustainable Development being the lead organisations on this work. Consequently since the indicators identified by the EU and Blue Plan are somewhat based on the ground work made by the aforementioned organisations. Tables 1-3 list the indicators adopted by the
OECD, UN and Blue Plan respectively and clearly illustrate the similarity in approach. Since the EU list is identical to that adopted by the UN, the indicators are presented by one set in Table 2.
2.3 Each organisation has identified particular themes related to economic activities.
These include a set of indicators on the general economic performance of a country and then sets of indicators for particular economic activities. The UN
CSD set is more of a global nature in that they address the general economy of a
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Economic Activities and Sustainability country focusing only energy and the manufacturing industry. The themes and indicators adopted by the EU are identical to the UNCSD. The OECD indicators identified three main sectors, namely Energy, Transport and Agriculture, whereas the Blue Plan set is more holistic and includes Fisheries, aquaculture, mining and
Industry, Services and Commerce as well as Tourism.
2.3 The OECD has adopted the Pressure - State - Response (PSR) Model as the basis for identifying the set of environmental indicators. Indicators are based on their policy relevance , analytical soundness and measurability . With respect to economic activities, the OECD has modified the PSR model to identify a set of sectoral indicators . The main function of this set of sectoral indicators is to promote integration of environmental concerns into sectoral policy making: e.g. transport-environment indicators, energy-environment indicators and agricultural indicators.
2.4
2.5
Sectoral indicators have been organised into three types: i. indicators to reflect sectoral trends and patterns of environmental significance and related driving forces; ii. indicators to reflect interactions between the sector and the environment , including positive and negative effects of sectoral activity on the environment (i.e. direct pressures, such as pollutant releases and resource use, and related effects and resulting environmental conditions, such as ambient concentrations of pollutants and population exposure), as well as effects of environmental changes on sectoral activity ; iii. indicators to reflect economic linkages between the sector and the environment, as well as policy consideration. This category includes environmental damage and environmental expenditure, economic and fiscal issues and trade issues .
The United Nations Commission on Sustainable Development (UNCSD) approved a work programme on indicators of sustainable development in 1995. A set of approximately 130 indicators was identified, using the Driving Force - State
- Response Framework . Driving Force indicators represent human activities, processes and patterns that impact on sustainable development. State indicators indicate the ‘state’ of sustainable development and Response indicators indicate policy options and other responses to changes in the state of sustainable development. A total of 24 economic indicators have been identified, which have been categorised into four sets.
2.6



The MAP/Blue Plan list of indicators is based on the UNCSD set and in effect has adopted 40 from that list. The Blue Plan list is based on a selection of social, economic and environmental data both on the global as well as the
Mediterranean level. Therefore issues such as erosion and desertification, over fishing as well as tourism development, have all been addressed. The indicators aim to provide information on:
The State of the environment and social, economic and ecological components of development and changes observed;
Pressures , which affect the balance between development and development;
Economic, political and institutional responses that aim to reduce these pressures and improve the situation.
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Economic Activities and Sustainability
5

Table 1 List of SIs identified by OECD
S ECTOR
Gross Domestic
Product
Consumption
T HEME I NDICATOR

GDP in total

GDP per capita
 the change in GDP compared to the change in population over the same period
Private Consumption by households and private non-profit institutions serving
 consumption as a percentage of GDP
 consumption per capita households as well as Government
Energy
Transport
Agriculture consumption of the following:

Private transport

Leisure and tourism

Energy

Use of package goods

Waste production

Demand for environmentally friendly goods
Trends in energy intensities
Energy mix
Energy prices for industry and
 energy supply per unit of GDP and per capita
 primary energy supply as a percentage of total energy supply
 changes in real energy end-use prices households
Road traffic and vehicle intensities intensity of use of nitrogen and
 vehicle numbers per capita and per kilometre of road
 length of road and motorway network per square kilometre of land area
 the relative price and taxation levels of diesel fuel and leaded and unleaded petrol
 the market share of unleaded petrol
 consumption in tonnes of active ingredients (N and P per sq km of agricultural land) phosphate fertilisers
Livestock densities intensity of use of pesticides
 the number of head of cattle, pigs, sheep and goats per sq km of land
 the amount of N and P generated by livestock manure per sq km of agricultural land
 apparent consumption or sales in tonnes of active ingredients per sq km of agricultural land
Table 2 List of Sis identified by the United Nations Commission for Sustainable Development and also adopted by the EU
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Economic Activities and Sustainability
Indicator Purpose i. International co-operation to accelerate sustainable development in countries and related policies
GDP per capita This indicator is a basic economic growth indicator and measures the level and extent of total economic output. It reflects changes in total production of goods and services.
Net investment share in GDP (%) The rate of investment measures the stimulus to economic development, reflecting the infusion of requisite capital to finance the development process. It is obtained by dividing gross production capital formation by GDP, b oth at purchasers’ prices.
The sum of exports and imports of goods and services as a ratio of GDP measures the openness of a country’s economy to international trade. Sum of exports and imports as a percent of GDP
Environmentally adjusted Net
Domestic Product (EDP) per capita
This indicator is obtained by deducting environmental costs from Net Domestic Product and dividing it by the total population
Share of manufactured goods in total merchandise exports
The percentage share of manufactured goods in tot al merchandise exports is meant to represent a country’s access to and participation in the global markets for manufactured goods. ii. Changing consumption patterns
Annual energy consumption per capita
The amount of energy consumed in a given year.
Percentage share of the contribution to manufacturing value-added of those industries that are intensive in the use of non-renewable resources Share of natural-resources intensive industries in manufacturing valueadded
Proven mineral reserves Orebodies or deposits economically viable for extraction which have been sampled sufficiently enough to make reliable estimates of spatial extent, tonnage and average grade.
Proven fossil fuel energy reserves
Lifetime of proven energy reserves
Intensity of material use
The availability of fossil fuel energy resources that can be recovered with reasonable certainty in the future, under existing economic and technical conditions.
The ration of energy reserves remaining at the end of any year to the production of energy in that year
The consumption volume of primary and secondary materials per unit of real Gross Domestic Product; calculated for one commodity at the country level. Provides a measure of long-term trends in changing consumption patterns of the key non-fuel, non-renewable natural materials.
Measuring the contribution of the manufacturing sector in total production gives an indication on the state of the economy. Share of manufacturing value-added
GDP (%)
Share of consumption of renewable energy resources (%)
The proportion of energy mix between renewable and non-renewable energy resources. iii. Financial resources and mechanisms
Net resource transfer/GNP The ratio of aggregate net resource transfers (long-term) to GNP helps to assess the availability of long-term external finance to a country.
It measures the size of flows that are both concessional and aimed mainly at promoting development and welfare of developing countries. Total Official Development
Assistance (ODA) given or received as a percentage of GNP
Debt/GNP
Debt service/export
The ratio of total external debt to gross national product is a measure of the degree of indebtness, and the indicator helps to assess the external debt situation (and debt carrying capacity) of a country.
The ratio of total debt service to exports of goods and services, including worker’s remittances helps to assess the external debt servicing capacity of a country.
Environmental protection expenditures as a percentage of
GDP
Environmental protection expenditures are actual expenses incurred to prevent, reduce and eliminate pollution as well as any other degradation of the environment.
Amount of new or additional funding This indicator signifies movement toward meeting the incremental costs of implementing Agenda 21.
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Economic Activities and Sustainability for sustainable development given/received since 1992 iv. Transfer of environmentally sound technologically, cooperation and capacity-building.
Capital goods imports Total value of capital goods imports measures the transfer of embodied technology.
Foreign direct investments (FDI) The value of net flows of foreign direct investment is meant to represent the technology transferred through the activities of foreign firms in an host country.
The contribution of environmentally sound technology in the transfer of embodied technology. Share of environmentally sound capital goods imports in total capital goods imports
Technical cooperation grants The value of technical cooperation grants is meant to represent the technology transferred through non-commercial sources.
Table 3
List of SI’s Identified by the Blue Plan (UNEP)
Thematic Framework Indicator
E CONOMIC A CTIVITIES AND S USTAINABILITY
Distribution of GDP (Agriculture, Industry,
Services)
Definition
Contribution by each business sector to the Gross Domestic Product as a %
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Economic Activities and Sustainability
Global Economy
Agriculture
Fisheries aquaculture and
Mines and Industry
Services
Commerce and
Foreign direct investment (FDI)
External debt/GDP
Saving/investment
Public deficit/GDP
Current payments/GDP
Employment Distribution (Agriculture, Industry,
Services)
Use of Agricultural Pesticides
Use of Fertilisers per hectare of agricultural land
Share of irrigated agricultural land
Agriculture water demand per irrigated area
Arable land per capita
Rate of food dependence
Annual average of wheat yield
Water use efficiency for irrigation
Value of halieutic catches at constant prices
Number and average power of fishing boats
Fishing production per broad species groups
Production of aquaculture
Public expenditures on fish stock monitoring
Industrial releases into water
Intensity of material use
Number of mines and quarries rehabilitated after exploitation
Turnover distribution of commerce according to the number of employees
Share of merchant service to the enterprises
Net investments made in a company operating in a country other that that where the investor comes from
The ratio of total external debt to GDP
The ratio of gross national savings to gross national investment
The national debt for the central government compared annually to GDP
The balance of current account payments in a country compared each year with GDP
The respective proportion of the active population in each of three major economic sector: framing, industry and services, out of the total active population.
NB The proportion for tourism is desirable but remains difficult to pick out.
The use of pesticide per unit of agricultual land two sub-indicators:
 the quantity of mineral nitrogen used per hectare of agricultural lands (temporary and permannet crops);
 the quantity of mineral phosphorus used per hactare of agricultural land (temporary and permanent crops)
The land area under irrigation as a percentage of total agricultural land area
The ratio of irrigation water consumption (withdrawals) to the irrigated area
The ratio of arable land area to total population
The amount of food products imported nationally over the amount consumed nationally for those same food products in the course of one year
Average quantity of wheat harvested annually in a country and related to the area growing wheat during the same period
Two sub-indicators:
E1: the physical efficiency of networks for carrying and distributing irrigation water
E2: the efficiency of irrigation in each plot
Total annual value of sea fish catches
The number and avareage power of registered fishing boats anually
Qauntities of sea fish caught each year that live in the open water (pelagic) or close to the bottom
(demersal) in the Mediterranean
The quantity of sea fish produce by fish farming companies set up in the country
The annual amount of public expenditure made to assess and monitor sea fish stock
The daily quantity of pollutants contained in industrial (untreated) waste discharges
Total annual consumption of virgin metals (by volume) per unit of GDP. Five reference metals: aluminium, iron, copper, lead and nickel.
The proportion of mine and quarries that have been subjected to reclamation or a rehabilitation projet after they have been worked out.
The respective proportions of the total annual turnover for trading companies by the main categories of staff.
The proportion of value added by companies providing services to other companies within the total added value of trading companies
The existence (or otherwise) of legislation limiting the set-up of hypermarkets in the country Existence of legislations on the hypermarket setting up restrictions
Energy intensity The proportion of total energy consumption per GDP unit per annum
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Economic Activities and Sustainability
Energy
Transport
Tourism
Energy balance Two sub-indicators:
 the spread of natural primary energy production by major source types: solid fuels, liquid fuels, gas fuels and primary electricity
 the spread of natural primary energy consumption by major source types: solid fuels, liquid fuels, gas fuels and primary electricity
The proportion of total energy consumption which is ensured by renewable energy resources Share of consumption of renewable energy resources
Average annual distance covered per passenger car
Structure of transport by mode
The average distance travelled each ye ar by the country’s passenger cars
Density of the road network
Share of collective transport
Number of nights per hundred inhabitants
The spread of journey’s per person within a country as a percentage over three modes of transport: road
(public and private), rail and air (internal flights)
The proportion of the total length of roads to the total area of the country
The ratio of the number of movements using collective transport on the total number of movement
Number of secondary homes over total number of residences
Number of bed-places per hundred inhabitant
Public expenditure on tourism development
Currency balance due to tourism activities
Public expenditure on tourism site conservation
The number of national and internationalovernight stays in hotels and similar establishments compared annually with the number of inhabitants in a country
The number of second homes to the total number of dwellings
The number of beds in hotels and similar establishments compared to the population annually
The annual amount of public expenditure (government and local communities) devoted to the development of tourist activities in the country
Number of international tourists per 100 inhabitant The number of arrivals by international tourists compared annually to the number of inhabitants in a country.
Share of tourism receipts in the exportations The proposrtion of international tourism income expressed as percentage of the export of goods and services in a country
The amount of net profits in a currency deriving from international tourism for a country
The amount of total net public expenditure allocated to the conservation, management or development of places of interest (cultural, historical and natural patrimony)
E XCHANGES AND C OOPERATION IN THE M EDITERRANEAN
International free trade zone and environment trade, Openness rate of GDP Total exports and imports of goods and services expressed as a% of GDP
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3.1
3.2
3.3
3.4
3.5
3.6
3.7
Most of the sustainability indicators addressing economic activities are relevant to the local situation in Malta, with some exceptions. The list of indicators suggested in this section is based on the main economic activities undertaken in the Maltese
Islands, taking into account the respective environmental issues associated with them. Table 4 below gives an indication on relative ease in data availability for the proposed indicators and possible sources.
The fact that Malta is a Small Island State is one major characteristic of the
Maltese Islands that affects the development of economic activities and their impacts on the natural environment. The issue of land availability needs to be considered when trying to adopt sustainability indicators; land take-up by economic activities has subsequent pressure on natural resources and biodiversity.
The report published by Friends of the Earth Malta in 1997 summarises the main themes that need to be addressed in terms of sustainability. These include Land use , Energy , Water , Wood and Non-renewables . All of these issues are related with the main economic sectors present in the Maltese Islands. Agriculture, quarrying and the development of infrastructure for manufacturing and the services industries take up land. Energy is utilised by all of the sectors in one form or another, and in Malta’s case a large portion of energy output is directed towards potable water production through desalination plants. Non-renewable consumption is mainly related to manufacturing produce. Although wood consumption per se is low paper consumption is high and very little is recycled
(FOE – Malta, 1997).
The maritime sector and its sustainable development have only been addressed with respect to marine pollution and mainly associated with sewage discharge; very little data is available on contamination from industrial discharge. The use of the marine environment for economic activities has been increasing over the last two decades with the development of the Malta Freeport, the establishment of bunkering sites, the introduction of aquaculture as well as the development of yacht marinas.
This diversification of economic activities into the marine environment is even being employed by other economic sectors such as tourism, where measures to boost the Cruise liner service are augmenting. Available data indicates that the majority of these sectors have been performing well and the trends seem to suggest that similar performance is expected in the future.
In view of these factors, a tentative list of possible sustainable indicators addressing economic activities in Malta has been drawn up based on the sets identified primarily by BluePlan. As a first attempt the list is exhaustive with a purpose to address most of the issues. Upon further analysis, particularly associated with data availability, there is a possibility that summary indicators are produced.
The main themes that have been identified include, global economy , land-use , consumption , energy , transport , agriculture , fisheries and aquaculture , non-renewables , services and commerce and tourism . Most of the proposed indicators can be measured through the data available from the National
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Economic Activities and Sustainability
Statistics Office as it is the main repository of all information emanating from the main economic sectors. Data relevant to particular sectors by be available from the relevant regulatory agency (as indicated in Table 4). These include the
Planning Authority, the Public Transport Authority, the Malta Tourism Authority and the Agriculture Department. It is possible that there may be some difficulties in obtaining data related to agriculture since not all the relevant data may have been collected.
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Table 4 Proposed list of Sis for Economic Activities in the Maltese Islands
Global Economy
Land-use
Consumption
Energy
Transport
Indicator
GDP in total
GDP per capita
Distribution of GDP per economic sector(agriculture, fisheries, industry, services including tourism)
External debt/GDP
Saving/investment
E
Public deficit/GDP
Current Payments/GDP
Employment distribution per sector
Share of manufactured goods in total merchandise exports
Environmental protection expenditure as a % of GDP
Share of environmentally sound capital goods imports in total capital goods export
Sum of exports and imports as a % of GDP
Percentage of land take up by each industry as a % of total land area
Private consumption by households and private non-profit organisation as a% of GDP and per capita of:
 private transport
 leisure and tourism
 energy
 use of packaged goods
 waste production
 demand for environmentally friendly goods
Government consumption as a% of GDP and per capita of :
 transport
 energy
 use of packaged goods
 waste production
 demand for environmentally friendly goods
Energy consumed per GDP unit per annum
Energy consumed per economic sector
Energy supply per unit GDP and per capita
Primary energy supply as a % of total energy
Share of consumption of renewable energy sources
Spread of natural primary energy production by major sources type ( solid, liquid gas fuels and primary electricity)
Spread of natural primary energy consumption by major sources type ( solid, liquid gas fuels and primary electricity)
Vehicle number per capita and per km of road
Length of road network per km 2 of land area
Relative price and taxation levels of Diesel, Leaded and unleaded petrol
D VD I Data Source
NSO
NSO
NSO
NSO
NSO
NSO
NSO
NSO
NSO
NSO
NSO
NSO
PA/MDC
MTA/NSO/PA
NSO
NSO
NSO
NSO
NSO
NSO
NSO
NSO
NSO/PA
PA
NSO
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Economic Activities and Sustainability
Agriculture
Fisheries
Aquaculture
Non-Renewables
Services commerce
Tourism and and
Market share of unleaded petrol
Average annual distance covered per passenger car
Share of collective transport
Use of agricultural pesticides per hectare of agricultural land
Use of fertilisers per hectare of agricultural land
Share of irrigated agricultural land
Agriculture water demand per irrigated area
Arable land per capita
Rate of food dependence
Number of heads of cattle, pigs, poultry, rabbits per km 2 of land
Value of sea fish catches at constant prices
Fishing production per broad species group (pelagic/demersal)
Production of aquaculture
Total material used (Aluminium, Iron, Copper, Lead, Nickel)
Number of quarries rehabilitated after exploitation
Percentage of quarried material used
Total Tonne Equivalent Units (TEU) of cargo handled at the Malta Freeport
Total Tonnage of fuel re-exported through bunkering operations
Number of nights per 100 inhabitants
Number of beds per 100 inhabitants
Number of international tourists per 100 inhabitants share of tourist receipts in exportation

E: Easy to compute; D: somewhat difficult to compute; VD: very difficult to compute; I: impossible to compute

** unconfirmed possible sources of data
NSO
PA/NSO**
PA/PTA**
NSO/Agric.Dept
NSO/Agric.Dept
NSO/Agric.Dept
NSO/Agric.Dept
NSO/Agric.Dept
NSO
NSO
NSO
NSO
NSO
NSO**
PA
NSO/PA**
NSO
NSO
NSO
NSO
NSO
NSO
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4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
The improvement and maintenance of the quality of human life are intertwined with development as it provides the mechanism that transforms the natural resources into the basic infrastructure requirements ancillary to urban and rural development.
A review of the current sustainability indicators that have been identified by the
OECD, MAP/Blue Plan, EU and UN has been undertaken for the purpose of this report. Although each organisation has identified a number of indicators relating to economic activities, not all have been clearly developed. The main approach adopted to establish indicators is through the State-Pressure-Response Model, which looks at establishing indicators that can highlight changes with respect to the environmental resource base, the sources of such changes and any actions that have been undertaken to overcome or mitigate impacts emanating from these changes.
Each organisation has identified particular themes related to economic activities.
These include a set of indicators on the general economic performance of a country and then sets of indicators for particular economic activities.
The fact that Malta is a Small Island State is one major characteristic of the
Maltese Islands that affects the development of economic activities and their impacts on the natural environment. The issue of land availability needs to be considered when trying to adopt sustainability indicators; land take-up by economic activities has subsequent pressure on natural resources and biodiversity.
The maritime sector and its sustainable development have only been addressed locally with respect to marine pollution and mainly associated with sewage discharge; very little data is available on contamination from industrial discharge.
The use of the marine environment for economic activities has been increasing over the last two decades. Available data indicates that the majority of these sectors have been performing well and the trends seem to suggest that similar performance is expected in the future.
In view of these factors, a tentative list of possible sustainable indicators addressing economic activities in Malta has been drawn up based on the sets identified primarily by Blue Plan. The main themes that have been identified include, global economy , land-use , consumption , energy , transport , agriculture , fisheries and aquaculture , non-renewables , services and commerce and tourism .
Most of the proposed indicators can be measured through the data available from the National Statistics Office. Data relevant to particular sectors by be available from the relevant regulatory agency however, there may be some difficulties in obtaining data particularly related to agriculture since not all the relevant data may have been collected.
As a first attempt the list is exhaustive with a purpose to address most of the issues. Upon further analysis, particularly associated with data availability, there is a possibility that summary indicators are produced.
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Economic Activities and Sustainability
BIBLIOGRAPHY
EU Commission ( 2001) Communication from the Commission: A Sustainable Europe for a
Better World. A European Strategy for Sustainable Development . Brussels.
Eurostat (1997) Indicators of Sustainable Development . European Comunities, Luxembourg
IUCN/UNEP/WWF (1991) Caring for the Earth: A Strategy for Sustainability Living . IUCN
Gland, Switzerland
Mediterranean Commission on Sustainable Development (1999) Indicators for Sustainable
Development in the Mediterranean Region: Introductory note . Blue Plan
Mediterranean Commission on Sustainable Development (2000) Indicators for Sustainable
Development in the Mediterranean Region: Glossary . Blue Plan
Ministry for Economic Services. (2000) Economic Survey Jan-Sep 2000 . Economic Policy
Division, Malta
OECD (1998) Towards Sustainable Development: Environmental Indicators .
Pearce, D., Moran, D (1994) The Economic Value of Biodiversity . Earthscan Publications Ltd,
UK
United Nations Sustainable Development: Indicators Methodology Sheets . (1999).Online. http://www.un.org/esa/sustdev/indisd/english/econ.htm
. 3 June 2001 http://www/sustainable-cities.org/indicators
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