Table 5.1 Food group shares (%) of household calorie intake for Malawi

Changes in ConsumptionPatterns: ANOVA

Source: Babu and Sanyal (2009)

Consumption Patterns: Importance

1. Total consumption accounts for more than two-thirdsof national income in many countries, largestcomponent having implications for the state of theeconomy.

2. Important to know changes in pattern ofconsumption since it reveals changes in economicwelfare and living standards – a measure of economicperformance. Finally,

3. Facilitates understanding the price responsiveness ofconsumption required for microeconomic policyissues, which include the measurement of distortions,optimal taxation and the treatment of externalities.

Changes in Consumption Patterns and Food Policy

Consumption Pattern & Food Security

1. Food security = f(Per capita availability of food , Changesin the composition of diet)

•Causes of changes in diet:

Demographic and epidemiological transitions

Demographic transition occurs due to a shift from a pattern ofhigh fertility and mortality to one of low fertility and mortality,

Epidemiological transition occurs due to a shift from a patternof high prevalence of infectious disease associated withmalnutrition, to one of high prevalence of chronic anddegenerative diseases associated with urban lifestyles.

Nutritional outcomes of such transitions: Changes in bodycomposition and morbidity.

Changes in Consumption Patterns and Food Policy

Food Consumption Patterns: Determinants

•Food consumption:

Quantity and quality of food intake byhouseholds/individuals

Good proxy: calorie or nutrient intake

Economic Devt & associated changes in CP

 In addition to income & expenditure, rural–urban migration, changes in demographicstructures and improvements in education,transport and communications, and marketinginfrastructure would affect CPs.

Changes in Consumption Patterns and Food Policy

Percentage distribution of caloriesource by level of per capita GNP

Changes in Consumption Patterns and Food Policy

ANOVA

•ANOVA: To test if differences exist between two ormore population means.

•Populations pertain to interval data.

•Procedure: Analyze sample variance.

•Two variables: 1 Nominal , 1 Quantitative.

•Suppose categorical variable has only 2 values, thenwe use 2-sample t-test.

•Superiority of ANOVA: allows for 3 or more groups.

Changes in Consumption Patterns and Food Policy

Descriptive Approach

•Graphical investigation:

• Juxtaposed box plots

• Multiple histograms

•How far the differences between groups aresignificant depends on

• the difference in the means

• the standard deviations of each group

• the sample sizes

Changes in Consumption Patterns and Food Policy

ANOVA

ANOVA: Test of hypotheses about more than twopopulation mean parameters:

H0: The means of all the groups are equal.

Ha: Not all the means are equal

It doesn’t say how or which ones differ.

It can also be extended to multiple comparisons

Changes in Consumption Patterns and Food Policy

Assumptions

•Each population follows normal distribution

Verify by drawing histograms and/or normalquantile plots, or use assumptions.

Valid even with non-normal populations but notso with outliers.

•Standard deviations of each population areapproximately equal

Verify if the ratio of largest to smallest sample st.dev. is greater than 2:1.

Changes in Consumption Patterns and Food Policy

Normality Verification

•Options for verification:

• assumptions about population

• histograms for each group

• normal quantile plot for each group

•No robust method when it comes to smallsamples; hence, assume normality.

Changes in Consumption Patterns and Food Policy

Table 5.1 Food group shares (%) of household calorieintake for Malawi

Food group

Mean share

Standard deviation

Maize

63.66

38.71

Other grains

9.76

21.91

Roots/tubers

16.54

27.01

Meat, fish & eggs

4.91

16.43

Milk

1.56

7.73

Vegetables

1.98

9.92

Pulses

0.76

5.24

Note: The mean share of calories does not sum to 100 per cent since the calories from other food are notavailable.

Changes in Consumption Patterns and Food Policy

Descriptive Statistics

•Statistics: Mean and standard deviations of the foodshares from the various groups.

•As a proportion of the total household calorieintake, the mean share of maize was almost 64 percent - maize is the dominant staple food crop inMalawi.

•Roots and tubers (cassava, plantains and sweetpotato) (16.5 per cent of total calorie intake).

•Last: grains such as rice and sorghum.

Changes in Consumption Patterns and Food Policy

Table 5.2 Mean share of calories from various foodgroups by expenditure brackets

Per capitaexpenditurequartiles

Maize

Other grains

Roots/tubers

Meat, fishand eggs

Milk

Vegetables

Pulses

1 (Lowest)

62.12

11.1

15.03

8.64

1.51

1.05

0.42

2 (Lowermiddle)

72.17

6.75

13.52

3.64

0.64

1.73

0.36

3 (Uppermiddle)

64.8

8.11

15.45

4.43

2.75

1.88

1.58

4 (Highest)

57.3

12.3

21.97

1.97

1.27

3.4

0.72

Total

63.67

9.77

16.55

4.91

1.57

1.98

0.76

Changes in Consumption Patterns and Food Policy

Descriptive Statistics

•Maize: Major source of calories followed by rootsand tubers, and other grains (such as rice, sorghum).

•Consumption preferences similar across quartiles.

•For the higher expenditure groups, the share ofcalories from maize, which is a staple diet, declineswhile the share of calories from animal products,vegetables and dairy products increases; becausewith increase in incomes, households substitute abetter variety of food (in calorie and dietary content)compared to maize, which usually has lower dietaryvalue.

Changes in Consumption Patterns and Food Policy

Table 5.3 One-way ANOVA for share of calories acrossexpenditure quartiles

Sig.

Maize

3.565

0.014

Other grains

1.97

0.117

Roots/tubers

2.837

0.037

Meat/fish/eggs

5.09

0.002

Milk

1.82

0.142

Vegetables

1.59

0.191

Pulses

1.66

0.174

Changes in Consumption Patterns and Food Policy

Test of Hypothesis

•Reject the null hypothesis that the shares ofcalories from maize for the four expenditure groupsare the same at the 5 per cent level.

•Reject the null hypothesis that calorie shares ofroots and tubers and meat, fish and eggs forhouseholds in all the expenditure groups are thesame at the 5 and 1 per cent levels respectively.

•The groups for which the null hypothesis cannot berejected are other grains, milk, vegetables andpulses.

Changes in Consumption Patterns and Food Policy

Inference

•Malawi:

Most of the households consume maize as part of astaple diet in order to derive calories.

ANOVA: Calorie shares of maize for households indifferent expenditure groups are not the same.

Poorer households derive most of the calories fromcereals such as maize.

As income of the households increases, there isgreater substitution towards vegetables, milk andmeat, fish and eggs. Thus, there is a tendencytowards greater dietary diversity as incomeincreases.

Changes in Consumption Patterns and Food Policy