Introduction

Adequate and equitable access to animal-source protein is an important component of household food security and dietary quality. Differences in purchasing power, food prices, and economic conditions may affect not only the level of per capita animal protein consumption but also its distribution across socioeconomic groups. Therefore, jointly examining consumption trends, distributional inequality, and the responsiveness of consumption to changes in expenditure and prices across different economic groups is important for designing targeted food-security policies. Accordingly, this study focuses on expenditure deciles of urban Iranian households to examine patterns of per capita animal protein consumption, trends in its distributional inequality, and the economic factors associated with consumption.

Materials and Methods

The study uses panel data for 10 expenditure deciles of urban Iranian households over the period 1992–2024. The analyzed basket comprises red meat, poultry, fish, eggs, and dairy products, and per capita animal protein consumption was calculated based on the quantities consumed of these products. Distributional inequality was assessed using the Gini coefficient, Theil index, and the ratio of consumption between the tenth and first expenditure deciles. To provide a visual representation of changes in the distribution, Lorenz curves for per capita animal protein consumption were constructed for 1992, 2006, and 2024. The association between expenditure inequality and inequality in per capita animal protein consumption was also examined using a correlation coefficient. In the econometric analysis, following diagnostic testing and model selection, a fixed-effects panel model with Driscoll–Kraay robust standard errors was estimated. To investigate heterogeneity in consumption responses across expenditure deciles, interaction terms between the economic variables and expenditure-decile indicators were incorporated into the model, and marginal effects were subsequently calculated for each decile.

Results and Discussion

The results indicate substantial differences in per capita animal protein consumption across expenditure deciles, with higher expenditure deciles generally exhibiting higher consumption levels. The inequality measures and Lorenz curves indicate a decline in inequality in the level of per capita animal protein consumption over the study period, with the Gini coefficient decreasing from approximately 0.275 in 1992 to 0.202 in 2024. However, this decline cannot, by itself, be interpreted as evidence of improved nutritional equity or dietary quality, because the composition of the protein basket changed concurrently and the share of red meat declined. Thus, the observed reduction in quantitative inequality may partly reflect substitution among protein sources and does not necessarily imply an improvement in dietary quality. A positive and statistically significant association was also observed between expenditure inequality and inequality in per capita animal protein consumption. The final model results indicate that real per capita household expenditure is the most important economic determinant associated with per capita animal protein consumption. Expenditure elasticity was positive and statistically significant across all expenditure deciles, but declined from 0.816 in the first decile to 0.50 in the tenth decile, indicating greater responsiveness of animal protein consumption to changes in expenditure among lower-expenditure households. Price responses were also heterogeneous across deciles. The real price of poultry had a negative effect in all deciles, but the effect was statistically significant only in the first and second deciles. In contrast, the real price of red meat had a negative and statistically significant effect in the fourth through ninth deciles, with the absolute magnitude of the response increasing at higher expenditure levels. The real price of dairy products also exerted a negative and statistically significant effect in all deciles except the seventh and ninth, with greater price sensitivity among lower-expenditure households. Short-run changes in fish prices had a negative and statistically significant effect only in the second decile, while the price of eggs, for which slope heterogeneity across expenditure deciles was not supported, had a negative but statistically insignificant effect on per capita animal protein consumption. In the final specification, the independent time trend was statistically insignificant. Nevertheless, the post-2022 dummy variable was negative and statistically significant, indicating that per capita animal protein consumption during 2022–2024 was approximately 6.9% lower than in the pre-2022 period, after controlling for other factors.

Conclusion

The findings demonstrate that per capita animal protein consumption in Iran is strongly associated with household purchasing power, although the magnitude of this relationship varies systematically across the expenditure distribution. The greater responsiveness of lower-expenditure households to expenditure and to the prices of selected protein sources indicates their greater vulnerability to declining purchasing power and food-price increases. At the same time, the decline in quantitative inequality in animal protein consumption should not be interpreted as unequivocal evidence of improved nutritional equity, given the concurrent changes in basket composition. The significant reduction in consumption during 2022–2024 further indicates that economic and policy shocks may affect per capita animal protein consumption beyond the effects captured by observed expenditure and prices. Given the positive and significant expenditure elasticities and their greater magnitude among lower-expenditure households, targeted food assistance and measures to strengthen the purchasing power of these households may be more effective than broad-based interventions. Furthermore, given the significant price effect of poultry in the first and second expenditure deciles, reducing price volatility and maintaining affordable access to poultry should be considered in policies aimed at protecting protein access among lower-expenditure households. The greater price sensitivity of lower-expenditure households to dairy products also supports temporary and targeted assistance for essential protein-rich foods during periods of high inflation. Finally, given the decline in the Gini coefficient alongside changes in basket composition and the declining share of red meat, food-security policies should evaluate not only the quantity of consumption but also the adequacy and quality of the protein basket. The 6.9% decline in consumption during 2022–2024 further underscores the need for timely and targeted compensatory interventions during periods of price shocks and major economic reforms.

Keywords: Expenditure Deciles, Nutritional equity, Lorenz curve, fixed-effects model, Driscoll–Kraay