Rural market access and
nutritional outcomes in
farm households
William A. Masters
http://sites.tufts.edu/willmasters
Amelia F. Darrouzet-Nardi
http://sites.tufts.edu/ameliadarrouzetnardi
Friedman School of Nutrition, Tufts University
Joint A4NH/ISPC workshop on agriculture-nutrition linkages
22-23 September 2014
Market access and farm household nutrition
motivation | the global study | the DRC study
How do rural markets influence
nutrition outcomes in farm households?
1. Could improve or worsen nutrition, by various direct channels
a) Household income, wealth and purchasing power
b) Time allocation especially for women and children
c) Relative cost of access to safe and nutritious foods
2. Could alter the ag-nutrition relationship, by effect modifiers
a) Separates decision-making between farm and household
b) Alters resilience and consumption smoothing
3. Here we add to the long and old literature on #1
and introduce new work on #2b
4. Will present empirical results then implications
and start with a hypothesized causal model
Market access and farm household nutrition
motivation | the global study | the DRC study
A causal model of farm household decision-making
Rural markets give households additional options, allowing them
to overcome diminishing returns in working their own land
Other employment
(allows sale of labor to buy food)
Qty. of nutritious foods
(kg/yr)
Rural food markets
(allows sale of other goods to buy food)
Qty. of nutritious foods
(kg/yr)
Consumption
Consumption
Production
In self-sufficiency,
production =consumption
Production
Once farmers are actively trading,
production decisions are “separable”
from consumption choices,
linked only through purchasing power
That same separability applies whether
households are buying or selling,
and allows consumption smoothing over time
Qty. of farm household’s labor time
(hrs/yr)
Qty. of farm household’s other goods
(kg/yr)
Market access and farm household nutrition
motivation | the global study | the DRC study
Empirical identification of causal effects is difficult
• Market access tends to be closely correlated with productivity
and purchasing power, but relationship may not be causal
– Markets may arise and grow where people can use them
– People who can use them may move towards markets
• Here, we report on two ways to identify potentially causal links
between rural market access and farm household nutrition
– Globally, do subnational administrative regions with an earlier history of
urbanization have healthier maternal and child heights and weights?
– Within DRC, do farm households located closer to rural towns have
more resilience against seasonal shocks to child heights and weights?
• Both studies construct natural experiments, using time lags and
spatial variation in risk exposure to identify effects
Market access and farm household nutrition
motivation | the global study | the DRC study
The global study:
Does past urbanization help rural farmers today?
Log duration of urbanization around rural farm households
80
(with normal distribution superimposed, N=756 region-year observations, of regions that had reached 25% urbanization by 2000)
40
20
0
number of regions
60
Markets take time to develop,
and farmers’ regions vary widely
in how long they’ve had access
to towns and cities
-2
0
2
4
log(years before 2000 that the average cell in a region reached 25% urbanization)
(Mean year is 1988, earliest quartile is 1970)
Note: Data shown are for 756 subnational regions in 53 countries with DHS
surveys, using urbanization data from Motamed, Florax & Masters (2014)
6
Market access and farm household nutrition
motivation | the global study | the DRC study
Regions with earlier urbanization
have taller children now
Mean HAZ for rural farm children at each level of national income, by timing of urbanization
-1.45
-1.5
-1.55
-1.6
Child mean HAZ
-1.4
-1.35
(N=1171 observations from 143 DHS surveys in 57 countries with 520 subnational regions;
dashed line shows subnational regions that reached 25% urbanization before 1995
6
6.5
7
7.5
8
Log of World Bank GNI at PPP prices
8.5
9
Market access and farm household nutrition
motivation | the global study | the DRC study
Regions with earlier urbanization
have heavier children now
Mean WHZ for rural farm children at each level of national income, by timing of urbanization
-.4
Child mean WHZ
-.2
0
(N=1171 observations from 143 DHS surveys in 57 countries with 520 subnational regions;
dashed line shows subnational regions that reached 25% urbanization before 1995
-.6
For rural farm children, being in a region with more
established towns and cities is associated with
a very large weight advantage, and
a small significant height advantage
6
6.5
7
7.5
8
Log of World Bank GNI at PPP prices
8.5
9
Market access and farm household nutrition
motivation | the global study | the DRC study
The DRC study:
Does proximity to town confer resilience
against seasonal shocks?
• At each farm location, the timing of a child’s birth exposes them
differently to agroclimatic risk factors for malnutrition and disease
• The DRC is distinctive in that households vary widely in distance to
towns and also in exposure to seasonal risks
– We ask whether birth during and after wet seasons is harmful,
• For more remote households with less access to markets and services,
• In regions with more seasonal variation in rainfall
– Birth timing in “placebo” regions without seasons should have
no effect
Market access and farm household nutrition
motivation | the global study | the DRC study
Birth timing creates a natural experiment
• The “treatment” is having a distinct wet season (if there
is one) occur during late pregnancy and early infancy
– This is a particularly sensitive time for child development
– Wet seasons are a hungry period with poorer diets
– Wet seasons facilitate water- and vector-borne disease
• Market access may be protective
– Households can trade to smooth consumption
– Households can access health and other services
• We expect no effect of birth timing, and no protection
from market access, in regions with uniform rainfall
Market access and farm household nutrition
motivation | the global study | the DRC study
Analytical design: Spatial difference-in-difference
Household location and child birth timing
Region has a distinct wet season?
(= farther from the equator)
Child was born in or after wet season?
(=Jan.-Jun. if lat.<0, Jul.-Dec. otherwise)
Household is closer to town?
(=closer to major town)
Hypothesized effect of birth timing:
No
(“placebo”)
Yes
Yes
(at risk)
No
Yes
No Yes
(protected?)
Neg.
Yes
No
No Yes No Yes No
None
Note: To test our hypothesis that market access protects against seasonality, the identifying
assumptions are that birth timing occurs randomly between seasons (tested), and that
seasonal risk factors would have been similar in the absence of towns (untestable).
Market access and farm household nutrition
motivation | the global study | the DRC study
Market access is measured by travel cost
weighted distance to the nearest major town
Darker cells
(100m2)
have better
market access.
Market access and farm household nutrition
motivation | the global study | the DRC study
Seasons depend on rainfall and temperature
equator
At the equator, average monthly rainfall
fluctuates from 100 to 200 mm, and
average monthly temperature
fluctuates from 24 to 26 degrees Celsius.
Market access and farm household nutrition
motivation | the global study | the DRC study
“Winter” is a drier period, farther from the equator
equator
Latitude -6
Away from the equator, there is a drier,
colder winter, here May through August.
Market access and farm household nutrition
motivation | the global study | the DRC study
In the other hemisphere, winter is 6 months later
Latitude +4
equator
Here in the Northern Hemisphere, the
drier season occurs from November
through February.
We split the data into groups by risk exposure..
All Children
N=2806
Child status
HAZ
WAZ
WHZ
Age (mos.)
Sex (% boys)
Household
Wealth quint.
Dist. to town (km)
Environment
Conflicts
Lat. (abs val.)
Jan.-June
No Seasons
N=650
Jan.-June
Seasons
N=903
July-Dec.
No Seasons
N=563
July-Dec.
Seasons
N=690
-1.47 (1.86)
-1.51 (2.02)
-1.51 (1.75)
-1.61 (1.92)
-1.26 (1.80)
-1.20 (1.38)
-1.09 (1.42)
-1.34 (1.31)
-1.17 (1.46)
-1.13 (1.34)
-0.38 (1.33)
-0.22 (1.39)
-0.53 (1.21)
-0.24 (1.41)
-0.45 (1.31)
29.16 (16.53) 28.81 (16.82) 28.53 (15.80) 29.70 (17.10) 29.88 (16.69)
49.4%
47.8%
49.8%
47.9%
51.4%
2.9 (1.42)
64.8 (52.1)
2.61 (1.25)
70.1 (47.9)
3.02 (1.48)
59.6 (51.9)
31.28 (66.9)
4.31 (2.64)
66.53 (97.82)
1.99 (1.16)
9.29 (19.47)
6.14 (2.01)
2.67 (1.26)
71.6 (45.3)
3.19 (1.51)
60.8 (59.8)
48.57 (84.24) 12.74 (22.99)
1.98 (1.17)
5.99 (2.02)
Note: Mean (standard deviation). Jan-June births are actually Jul.-Dec. births if
the child was born in the Northern Hemisphere (N=418). Conflicts are total
number of incidents between 2001 and 2007 in the respondent’s grid-cell of
residence.
We see a strong and significant “treatment effect” of
household remoteness in areas with seasons.
(1)
(2)
(3)
(4)
HAZ
No Seasons
0.000
0.165**
WHZ
Seasons
0.002
0.102***
WHZ
No Seasons
-0.000
-0.010
VARIABLES
Conflicts
Wealth quintile
Units/type
Cumulative days
Categorical
HAZ
Seasons
0.005**
0.152**
Remote
Born Jan.-June
Born Jan.-June*Remote
Child is male
Constant
Binary
Binary
Interaction
Binary
Constant
-0.434**
-0.363***
-0.407**
-0.192*
-0.149
0.338
0.141
0.407*
-0.192**
0.043
0.010
-0.0534
-0.144**
-0.097
0.520*
0.353
0.297*
0.075
-0.195**
0.490
Observations
R-squared
Number of regions
N
R2
N
1,593
0.154
10
1,213
0.155
7
1,593
0.082
10
1,213
0.035
7
Note: Age controls suppressed; Jan-June births are actually Jul.-Dec. births if the
child was born in the Northern Hemisphere (N=418); robust pval in
parentheses; errors clustered by region (N=11); *** p<0.01, ** p<0.05, * p<0.1
Among our robustness checks, we do placebo tests for
desirable outcomes that could not be caused by birth timing
No effects and large variances
where no effect is expected
1.5
1
0.5
0
-0.5
-1
-1.5
HAZ
WHZ
mother's
education (yrs)
mother
currently
working?
(binary)
mother's
father's
years lived in
size of
weight (kg) education (yrs) interview
household (#
location
of people)
altitude (m)
Note: Data shown are coefficient estimates and 95% confidence intervals for average treatment
effects in our preferred specification (Table 5), for our two dependent variables of interest
followed by seven placebo variables for which no effect is expected, due to the absence of any
plausible mechanism of action.
Market access and farm household nutrition
motivation | the global study | the DRC study
Conclusions
• From these data,
– Globally, farm households in subnational regions with a
longer history of urbanization have better nutritional
status
– Within DRC, farm households that are closer to towns
are more protected from seasonal shocks to nutritional
status
• These results add to the large and diverse
literature on farmers’ use of markets
– New data will permit many new tests to refine results
– But the importance of market access has strong
implications for agriculture-nutrition actions
Market access and farm household nutrition
motivation | the global study | the DRC study
Implications for policies and programs
• At a given level of household and community resources, facilitating
market access can
– Raise levels of nutritional status
– Improve resilience to shocks
• Farm households can use markets in many different ways
– Specialization and trade, to overcome diminishing returns on the farm
– Consumption smoothing, via separability of production & consumption
– Access to public services
• Future work may be able to distinguish among uses
– But various uses are naturally bundled together in related transactions
– And in any case policies and programs to ease market access cannot
prescribe what households do, just allow them to do it more easily!