_ANDR EE_<sup>_ ́_</sup> _DECEMBER - 2021_ _2_ Low inflation and price stability have historically been associated with improved growth and development outcomes (The World Bank, 2019; Ha et al., 2019b,a). Inflation dis-proportionally taxes the purchasing power of low incomes (Easterly and Fischer, 2001), which is in contrast with the proportional income effects of economic growth itself (Dollar and Kraay, 2002). As such, price stability and low inflation are crucial to achieve the Sustainable Development Goals and price data are critical for economic monitoring.

Food prices specifically play a critical role in determining the immediate ability of households to consume food (Andreyeva et al., 2010; Waterlander et al., 2019), and the capacity of farmers to plan the investments needed for reliable future production of food (Koomen et al., 2015; Andr ́ee et al., 2017; Diogo et al., 2017). Food price inflation thus serves as an important metric to inform economic policy and is closely watched by both economists and humanitarians during times of financial turmoil and economic crisis.<sup>1</sup> The traditional figures on inflation used for these purposes have primarily been produced at an aggregate level using data from few, highly urbanized, areas. As such they do not directly describe price evolution in rural or poverty-stricken areas, or in regions where vast populations are internally displaced and live in fragile situations.<sup>2</sup> For example, food crises are often characterized by great spatial heterogeneity and geographic specificity (Maxwell et al., 2020), while traditional price indicators do not provide insights beyond the major (urban) markets where prices are formally measured.<sup>3</sup> Traditional indicators are also often produced with delay, or not at all, particularly during crises when economic variables deteriorate rapidly.<sup>4</sup> Recognizing these limitations, international institutions have invested heavily

> 1The significance of price inflation as a signal of deteriorating food security can be highlighted by noting that the recent crises in South Sudan and the Republic of Yemen are characterized by high inflation. Historically, the Bengal famine of 1943 followed after a period of hyper-inflation, starvation in the Weimar Republic occurred alongside record hyper-inflation, the 1980 Uganda famine occurred after double to triple digit inflation rates, the 1992 famine in Southern Somalia was preceded by a year of triple-digit inflation, and the 1998 famine in southern Sudan was preceded by years of double digit inflation. The use of food price indicators to track famine risks is documented more substantively by Seaman and Holt (1980); Cutler (1984); Khan (1994); Andr ́ee et al. (2020); Wang et al. (2020).

> 2Naturally, there are other critiques around inflation calculations, some as old as the methodologies themselves. Some accusations about both up- and downward biases are discussed by Reinsdorf et al. (2009). Often, conflicting views on inflation can be traced back to differences in (baskets of) goods and data sampling locations, and so for some applications improved clarity can be gained by more narrowly defining indexes, which the results of the paper may also help enable.

> 3See also the recent economic update for South Sudan (World Bank, 2021). The work compares food prices subnationally and finds that increasing prices are the most significant factor driving recent food insecurity but documents strong spatial heterogeneity in both market price dynamics, as well as relations to food insecurity, and provides examples of markets where prices are more sensitive to localized shocks.

> 4For instance, the International Finance Statistics (IFS) data base of the IMF reports monthly price data at Consumer Price Index (CPI) component level, but few developing countries report food price data without substantial delays. Of the 25 countries analyzed by the paper, none presently reports real-time monthly official food price data; half had not reported food price data going back 12 months. Annual statistics are similarly far from complete. Of all countries in the World Bank’s WDI, only 60% (40% of the analyzed countries) had an inflation figure for the most recent 2019–2020 period. The IFS data reported similarly on only half of the countries. This was last checked on August 31, 2021; WDI data identifier FP.CPI.TOTL.ZG, and IFS data identifier PCPI ~~P~~ C ~~P~~ P ~~P~~ T.