US food waste revisited: a reproduction with public data

Hall et al. (2009) estimated US food waste as the difference between the per-capita food supply in FAO food balance sheets and the food intake implied, through an energy-balance model, by the rise in mean adult body weight. They reported that waste grew by about 50% from 1974 to 2003, to more than 1,400 kcal per person per day, and from about 30% to almost 40% of the supply. No code or data accompanied the paper. I re-implemented the model from its printed equations and re-ran it with public inputs: NCHS mean body weights (published tables for 1971–1994, NHANES microdata thereafter) and the current FAOSTAT food balance sheets. The calculation reproduces: the model coefficients came out at 9,103 kcal/kg and 22.1 kcal/kg/d (published 9,100 and 22). Waste rose from 929 to 1,459 kcal per person per day (57%), and its share of supply from 30.7% to 38.6%. The rise survived every input and parameter check, but the level did not: the 1974 share ranged from 22% to 37% depending on assumed baseline intake and whether children were counted. Extending the series to 2023, the wasted share peaked at 39.0% in 2002 and 2005, fell to about 35% in 2014–2017 (35.2% in 2017) and returned to 38.6% in 2023. The change from 2003 to 2023 was +0.0 percentage points (95% parameter-uncertainty interval −1.2 to +1.0; −0.2 with 2022 as end year). The original's arithmetic holds, but the waste it reports is a residual, and the 1974–2003 climb did not continue. Preprint, not peer reviewed. Also published at https://x9m8.com/food-waste-revisited/. The zip file contains the code, results and the two independent audits.