Will Masters, Tufts University Expert consultation on trade and nutrition 15-16 November 2016, FAO Headquarters, Rome http://www.fao.org/economic/est/est-events-new/tradenutrition/en/

1. Measuring the cost of nutritious diets:
Results for diet diversity
in Ghana and Tanzania
Will Masters
Friedman School of Nutrition Science & Policy, Tufts University
www.nutrition.tufts.edu | http://sites.tufts.edu/willmasters
Presentation at the FAO Expert Consultation on Trade and Nutrition
15-16 November 2016

2. New price indexes
• Indicators of Affordability of Nutritious Diets in Africa (IANDA)
– Project funded by UKAid through its program on Innovative
Methods and Metrics for Ag-Nutrition Actions (IMMANA),
managed by LCIRAH (LSHTM, SOAS) and Tufts University
– Project led by Jennie Coates and Anna Herforth,
with Rebecca Heidkamp (Johns Hopkins University),
Daniel Sarpong (University of Ghana),
Fulgence Mishili and Joyce Kinabo (Sokoine University)
– Today’s results are with Yan Bai (PhD student at Tufts)
Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps

3. But is
nutritious food
also becoming
less expensive?
Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps
What do food price indexes
tell us about the cost of nutritious diets?

4. Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps
Existing food price indexes
are weighted by market value
The FAO Food Price Index is a measure of the monthly change in
international prices of a basket of food commodities. It consists of
the average of five commodity group price indices, weighted with
the average export shares of each of the groups for 2002-2004.
Total of 23 commodities (73 prices), in 5 groups:
• Cereals
-- wheat (11), maize (1), rice (16)
• Oils/Fats
-- soybean, sunflower, rapeseed, groundnut, cottonseed,
copra, palm kernel, palm, linseed, castor (1 each)
• Dairy
-- whole milk powder, skim milk powder, cheese (2 each),
cheese (1)
• Meat
-- poultry (13), beef (7), pork (6), sheep (1)
• Sugar
-- sugar (1)
To measure “world prices”, the FAO aims to include traded foods

5. Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps
Food price trends and fluctuations
differ by level of value added
To measure cost of living (or output),
national accounts aim to include all goods & services
Food away from home
Food at home
Processed food & feed
Unprocessed food and feed
Source: US. Bureau of Labor Statistics, downloaded 12 November 2016.
Definitions and chart data are available at http://myf.re/g/aPV1
Consumer price indexes,
weighted by expenditure shares
Producer price indexes, weighted by market sales

6. Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps
What is the cost of a nutritious diet?
• Need nutritional values, rather than market values
– Previous subsistence indexes focus on dietary energy
• undernourishment, to maintain weight and physical activity
cost of staple foods or calories
– Today will focus on cost of dietary diversity
• beyond staples, foods with more nutrients and other attributes
=> cost of specific foods or food groups
– Next step will be cost of nutrient adequacy
• account for quantities, to reach recommended dietary intake
=> cost of nutrients
– Then include cost of other healthful or harmful attributes
• dietary guidelines, with upper as well as lower limits
=> cost of attributes (+ for beneficial, - for harmful)

7. Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps
Possible indexes of nutritional value
• For hunger and dietary energy, a long history and wide use
– Playfair (1821) chart of wheat prices and wages for 1565 to 1821
– Sukhatme (1961) and FAO’s Prevalence of Undernourishment in calories
– Drewnowski (2004) measure of energy cost ($/kcal) and density (kcal/kg)
• For nutrient adequacy, a long history and many specific uses
– Stigler (1945) linear programming to compute least-cost diets
– USDA Thrifty Food Plan for US nutrition assistance (1975, 1983, 1999, 2006)
– SCUK Cost of Diet tool (2009) and FANTA et al. Optifood (2012) for aid programs
• But diet diversity in terms of food groups of particular interest today
– DD takes account of all attributes in each food group, not just nutrients
– Grouping foods by attributes facilitates dietary surveys, where frequency of intake
over 24hr (or 7d) is feasible to recall, whereas quantities are usually unknown
– Number of food groups included in the diet has been linked to child height
(Arimond & Ruel 2004) and to women’s nutrient adequacy (Arimond et al. 2010)

8. Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps
Dietary diversity has overtaken nutrients
in popularity among nutritionists
Source: Calculated from https://books.google.com/ngrams, 12 November 2016
Relative frequency of use in English-language books, 1950-2008

9. Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps
Definitions of dietary diversity
• DD measures have evolved rapidly in recent years
– Nonlinearity in response
• From number of food groups (DDS) to minimum thresholds (MDD)
– Nonunitary households
• From household scores (HDDS) to individuals (children 0-5, women 15-49)
• Focus now is on Minimum Dietary Diversity for Women (MDD-W)
– Defined as eating at least 5 out of 10 food groups in previous 24 hrs
• Starchy staples (Grains, white roots/tubers, plantains)
• Pulses (beans, peas and lentils – includes soybeans)
• Nuts and seeds (higher fat than pulses, includes groundnuts)
• Meat, poultry and fish
• Dark green leafy vegetables
• Other vitA-rich fruits & vegetables
• Other vegetables
• Other fruits
• Eggs
• Dairy

10. Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps
Interpretation of dietary diversity
• MDD-W is primarily seen as a validated proxy for nutrient adequacy
– DD might also protect against excess intake of some foods
– DD can also be seen as a measure of real income and well-being
• MDD-W has a direct economic interpretation
– Within groups, all foods are perfect substitutes
– Each group provides a different mix of attributes
– Every group also contributes towards energy balance
– Groups can be ranked by cost towards total daily energy needed
– The least costly energy source (typically starchy staples) can meet few other needs
– People will include higher-cost energy sources in their diet to meet additional needs
– People who include at least five groups are likely to reach adequacy thresholds
• MDD-W food groups reflect common dietary substitutions
• Low-cost starchy staples: Grains, white roots/tubers, plantains
• Plant-based protein & fat: Pulses; Nuts and seeds
• Animal-sourced foods: Eggs; Dairy; Meat, poultry and fish
• Micronutrient-rich foods: Dark green leafy vegetables,
Other vitamin A-rich fruits & vegetables
Other vegetables, Other fruits

11. Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps
Computing the cost of dietary diversity
1.Obtain market prices
-- today’s data are from national statistical offices
(prices collected for national accounts, based on budget shares & uniformity)
-- another source could be agricultural market information services
(prices collected for market integration, based on role in long-distance trade or storage)
-- eventually sources could include humanitarian agencies
(prices collected for early warning (eg VAM), based on presence in remote markets)
2.Convert units of measure
-- all prices deflated to 2011 PPP prices based on PWT 8.1 data
-- quantities converted to dietary energy (kcal) or weight (kg)
3.Classify into MDD-W food groups
-- select the one lowest-cost item in each group
-- identify the fifth lowest-cost group

12. Results for Ghana
Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps
• Monthly averages across multiple markets, Jan. 2005 – Dec. 2014
• No prices available for dark green leafy vegetables or dairy
• The five lowest-cost are usually, in rank order:
• Starchy staples:
• Least costly is cassava or maize
• Pulses
• Least costly is usually soyabeans, occasionally cowpea
• Nuts and seeds
• Least costly is groundnuts
• Vit A-rich fruits and vegetables
• Least costly is mangoes, occasionally oranges, rarely tomatoes
• Other fruit
• Least costly is banana, occasionally pineapple
• The higher-cost groups are usually:
• Meat, poultry and fish
• Least costly is usually smoked herring, occasionally salted dried tilapia
• Other vegetables
• Least costly is usually onions, occasionally garden eggs
• Eggs
• Usually the most expensive food group
• Key questions:
• Is it OK to use cost/kcal to reach energy needs, vs. cost/kg as meal ingredients?
• Is it OK to count only five lowest-cost groups, vs. all food groups?

13. Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps
The least-cost starchy staple is usually cassava,
but sometimes maize
Sometimes maize can replace cassava
Note: if we ranked foods by weight ($/kg), the least cost starchy staple would always be cassava

14. Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps
The least-cost vegetable is onions in season,
otherwise garden eggs
Note: if we ranked foods by weight ($/kg), the least cost other veg. would usually be garden eggs
Garden eggs:

15. Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps
The least-cost fruit is almost always banana,
and occasionally orange or pineapple
Note: if we ranked foods by weight ($/kg), the least cost other fruit would usually be pineapple
orange pineapple
orange

16. Aggregating all food groups,
fluctuations 2009-11 then rise 2012-14
Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps
The price of just one food from the 5th group
The average of 8 foods,
one from each group

17. We would get different results when
ranking foods and food groups by weight
Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps
When we choose the heaviest (least cost in $/kg)
food from each group, the average of 8 foods
is more stable and has a different trend

18. Results for Tanzania
• Monthly averages across multiple markets, Jan. 2011 – Dec. 2015
• No prices available for dark green leafy vegetables or eggs
• The five lowest-cost are usually, in rank order:
• Starchy staples:
• Least costly is always maize
• Pulses
• Least costly is always soyabeans
• Nuts and seeds
• Least costly is always groundnuts
• Other fruits
• Least costly is usually avocado, occasionally green banana
• Meat, poultry and fish
• Least costly is always pork meat
• The higher-cost groups are usually:
• Dairy
• Least costly is fresh cow milk
• Vit A-rich fruits and vegetables
• Least costly is usually mangoes, sometimes papaya
• Other vegetables
• Least costly is onions
• Key questions:
• Is it OK to use cost/kcal to reach energy needs, vs. cost/kg as meal ingredients?
• Is it OK to count only five lowest-cost groups, vs. all food groups?
Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps

19. Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps
The least costly VitA-rich fruit or vegetable
is mangoes in season, otherwise papaya
Papaya is occasionally less costly than mango

20. Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps
Aggregating across all food groups,
rise in 2011-12 then relative stability to 2015
The price of just one food from the 5th group
The average of 8 foods, one from each group

21. Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps
In the TZ data, the cost of the 5th group
is far above the average of all 8 groups
012345
2011m1 2011m7 2012m1 2012m7 2013m1 2013m7 2014m1 2014m7 2015m1 2015m7 2016m1
Year/Month
White Maize Grains Round Onions Green Banana Avocado
Mangoes Papaya Fresh Cow Milk Soya Beans
Groundnuts Pork Meat MCDD ACOG
Figure 15. Minimium Prices by Foodstuffs and the MCDD/ACOG Indicators (per 1,000kcal)
The average of 8 foods, one from each group
Prices of the least-cost food in each group (energy basis)

22. Conclusions and next steps
Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps
• Creating a price index for the cost of a nutritious diet is challenging
– Need clear definition of “nutritious”: a quantity index
• Here, we use MDD-W
• Next, we will use RDIs
• Eventually, include attributes other than nutrients
– Need new kinds of data
• Here, we use prices from GH & TZ national accounts
• This is good enough for a pilot, not yet ready to guide policy or programs
• Pilot reveals data-collection priorities
– For this particular aspect of nutrition policy and programs
» Missing groups: green leafy vegetables, dairy, eggs
» Misfit definitions of groups: pulses vs. nuts/seeds
» Misfit foods within groups: meat/fish/poultry (in TZ case)
(For this index, would need least-cost item such as dried fish)
– For this and many other uses in nutrition policy and programs
» Food composition data, for items with market prices
» Dietary intake data, to test how intake responds to prices

23. Conclusions and next steps
(continued)
Measuring the cost of nutritious diets in Africa
motivation | method | ghana | tanzania | next steps
• How can economists meet demand for cost-of-nutrition data?
– Need new understanding of what a cost-of-nutrition index measures
• Not a cost-of-living index!
– A benchmark for least costly way to meet nutrition needs
• Relevant to actual choices, but neither descriptive nor normative
– Should fit only the envelope of actual behavior
» How close a fit? (e.g. purchases by weight, or for culinary reasons)
» Fit to whose needs? (what location, age/sex or other category)
– Need clear agreement on definition of nutrition needs
• So far we are focusing on MDD-W and RDIs, but…
– may need to measures that count gains above/below clinical thresholds
– may need measures of other attributes beyond energy & nutrients
=> a long and complex research agenda !

24. Data analysis:
Yan Bai (PhD student)
Data sourcing:
Daniel Sarpong (Ghana)
Fulgence Mishili (Tanzania)
Project leadership:
Jennie Coates (PI)
Anna Herforth (Co-PI)
Rebecca Heidkamp (JHU)
Joyce Kinabo (Sokoine)
Funding:
DFID, through IMMANA
Thank you!