Accurately identifying who in the population is the poorest of the poor is critical for developing efficient and effective poverty reduction strategies. A key part of this task is to compare household welfare across households of different sizes, compositions and sub-national locations. Yet the typical equivalence scales used in this process by most policymakers impose harsh and unrealistic assumptions on household behaviour and the extent to which households of different sizes realise economies of scale in consumption (CSE). These assumptions include the notion that household tastes are unrelated to income (homothetic preferences) and no substantial differences exist in the extent to which CSE can be realised across households located in different sub-national regions, time periods and gender compositions. This thesis focuses mainly on analysing the CSE associated with food consumption, labelled as FCSE, since expenditure on food represents the major share of household expenditure for poor households. The main objective of this thesis is to investigate how household characteristics and their behavioural choices affect the ability of these households to achieve FCSE, and thereby their poverty status, using Sri Lanka as a case study. In doing so, the relationships between FCSE and a number of household socio-economic and demographic characteristics and household behavioural choices are investigated. The characteristics considered comprise household size, location, income, and gender of the head of household; the behavioural choices considered comprise the decision to consume home-grown food, and the decision to adopt domestic technology to aid food preparation and consumption.