368 Selcuk Journal of Agriculture and Food Sciences http://sjafs.selcuk.edu.tr/sjafs/index ….Research Article…. SJAFS (2022) 36 (3), 368-374 e-ISSN: 2458-8377 DOI:10.15316/SJAFS.2022.047 Food Expenditure Pattern of Household in Delta State, Nigeria: Economic Rationality Essentials Osaihiomwan OJOGHO 1 , Osagie Stephen IMADE 1 1 Benin University, Faculty of Agriculture, Department of Agricultural Economics, Benin, Nigeria. 1. Intrоduсtiоn Consumption patterns contribute greatly to the social and economic policy of a country. For a developing country the consumption pattern is skewed towards food. In Nigeria, household expenditure on food and non-food items in 2019 was over N40 trillion with 56.5% spent on food items. Further analysis of food expenditure by households in 2019 showed that various foods consumed outside the home such as starchy roots, tubers and plantains, rice, vegetables, fish and sea food, grains and flours in that order were top in the list of household food items accounting for a combined 59.19% of food expenditure, 33.53% of total household expenditure on food and 24.8% of total household expenditure. Household expenditure on non-food items on the other hand were directed mostly at transport, health, education and services, rent and fuel and light, * Corresponding author email: o.ojogho@uniben.edu accounting for a combined 79.40% of non-food expenditure. Consumption pattern for Delta state in 2019 showed that the state had 48.08% non-food expenditure and 51.92% food expenditure in the total expenditure (National Bureau of Statistics, NBS, 2019). However, there are variations in the food consumption expenditure pattern across the country. These have been attributed to income of households and prices of food commodities subject to the demand that household food expenditure choice be explained by the theory only in terms of economic observables. In Nigeria, household demand analyses have focused on functional forms which embody more general properties with respect to food prices and household income. Studies have determine household demand on the assumption of utility maximization that derived derivative-type conditions on demand functions that are implied by particular utility functional forms (Ojogho ARTICLE INFO ABSTRACT Article history: Received date: 18.03.2022 Accepted date: 26.08.2022 Parametric utility model that predicts preferences of heterogeneous food consumers is flawed with issues of economic rationality. Using axiomatic preference indexes on food data from 459 household selected from a three-stage sampling procedure, the aim of the study was to check whether a finite set of price and demand observations made on household consumers in Delta state is rationalizable by some form of utility maximization that is common across all households. The study found heterogeneity in food consumption behaviour with evidence against rationality in utility maximization for food expenditure choices at Afriat Efficiency Index (AEI) of unity, violating the GARP, SARP, SGARP, HARP and CM outside the optimum AEI of between 0.536 and 0.982 inclusive. In three of the four food choice categories, households had below the Varian AEI threshold of 0.95. Particularly, household expenditure behavior in the State violated the GARP axiom of revealed preference at 0.018, 0.07, 0.104, 0.05, and 0.081 severity of violations for food in general, protein, carbohydrate, fats and oil, and fruits and vegetables sub-food categories respectively with 5-45% of inconsistent household behaviour. At AEI of unity, 14.30%, 4.79%, 11.43% and 45.04% of the households failed the zero tolerance in the carbohydrate, protein, fats and oil, and fruits and vegetables categories respectively. Only about three to six revealed preferences were found necessary to fully rationalise observed food expenditure choices in the State. Thus, not only are households irrational in utility maximization, there is unstable preference in food demand. Therefore, there is, in the aggregate, no exact one continuous, strictly increasing, piecewise strictly concave, skew-symmetric, and/or homothetic preference function that would completely rationalize households food consumption behaviour in Delta state. Keywords: Preferences AEI GARP SARP SGARP HARP CM