# **Appendix A : Data Description and Sources**

## **Domestic Prices**

Wholesale white maize prices in Tanzania are monthly averages, expressed in TZ shillings per kg, collected by Tanzania’s Ministry of Industry and Trade in 18 markets. These markets are grouped into five zones and cover the entire country. Data on domestic fuel prices and CPI are collected by Tanzania’s National Bureau of Statistics (NBS).

## **External Prices**

Wholesale white maize prices in Nairobi (Kenya), Randfontein (South Africa), and Nampula (Mozambique) are sourced from FAO GIEWS (http://www.fao.org/giews/english/ index.htm); U.S. Maize prices represent no. 2, yellow, f.o.b. Gulf ports. Crude oil price is the average of Brent (U.K. 38<sup>0</sup> API), West Texas Intermediate (WTI 40<sup>0</sup> API), and Dubai (Fateh 32<sup>0</sup> API) equally weighted. World prices for maize and oil were taken from the World Bank’s pink sheet (http://go.worldbank.org/4ROCCIEQ50).

## **Export Ban**

An export ban is represented by a dummy variable taking the value of 1 when the ban was effective and zero otherwise. The ban was effective during the following months: Jan— Dec 2005, Mar 2006—Jan 2007, Jan—May 2008, Jan 2009—Oct 2010, Jul 2011 (introduction was announced informally in Mar 2011)—Dec 2011 (lifting was announced informally in Oct 2011). This was sourced from FAO GIEWS, newspaper articles, and interviews with industry representatives.

## **Normalized Difference Vegetation Index anomaly**

Weather disturbances in this study were estimated using satellite-derived Normalized Difference Vegetation Index (NDVI) imagery over cultivated areas as a proxy. NDVI is derived from the visible and near-infrared portions of the electromagnetic spectrum and the contrast between the two provides a strong indication of vegetative health and plant productivity (c.f. Tucker (1979)). In an agricultural context, NDVI captured during the heart of the growing season, and thus anomalies of it from normal, have been shown related to crop productivity (Becker-Reshef et al. (2010); Johnson (2014); Brown (2014)). In other words, higher than expected values of NDVI during the growing season would be consistent with weather conditions that have been favorable to crop yields and, conversely, below normal NDVI values suggestive of lower than typical yields.

The NDVI data used in this research was collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor aboard the NASA polar orbiting satellite Aqua from July 2002 to July 2014. MODIS provided an NDVI estimate every eight days at an approximately 250 meter ground sample (pixel) resolution across the entire study area. To isolate the NDVI signal to only those areas where crops are expected the time series was ‘masked’ by the Croplands and Cropland/Natural Vegetation Mosaic categories found within the IGBP land cover classification (c.f. Loveland et al. (2000)). Next, to reduce potential pixel-level noise (both in time and space) and simplify the modeling efforts, the measurements were aggregated to monthly values at a 5 kilometer grid cell size. And finally, the values were spatially averaged further to each of study areas in order to directly link them with the economic data.

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