# Data Sources

We used district-level data for all 16 irrigated<sup>districts of Punjab, defined as those having at least</sup> 50% irrigated area. Together they account<sup>for over 90% of agricultural production in the Punjab.</sup> The district level data were then aggregated<sup>to the production system level for purposes of</sup> computing TFP. Production systems were<sup>defined based on: i) cropping intensity, and ii) the</sup> major summer (or kharif) crop during<sup>1980-81. Wheat is the dominant winter (or rabi) crop</sup> everywhere, accounting for over 80% of cropped<sup>area. Thus the districts of the province were</sup> divided into four commonly recognized systems<sup>based on the dominant summer (kharif) crop: 1)</sup> wheat-mixed summer crops (often maize<sup>or sugarcane), 2) wheat-cotton, 3) wheat-rice, and 4)</sup> wheat-mungbean (or wheat-fallow).<sup>9</sup> These systems represent quite different agronomic<sup>types</sup> from a cereal-legume or fallow system (more likely<sup>to be sustainable) to a continuous cereal</sup> cropping system (likely to be less sustainable-Hobbs and Morris, 1996). Livestock are important in all systems, especially cows and buffaloes<sup>for milk and meat.</sup> District level annual data were collected from<sup>secondary sources and the Statistical Division of</sup> the Federal Ministry of Food and Agriculture,<sup>at a high level of detail for the period 1966-94.</sup> The study includes 33 crops, 8 livestock products,<sup>six crop by-products, and 17 input categories.</sup> Inputs and outputs were valued at farmgate harvest<sup>prices, also collected or estimated at the</sup> district level.

Input categories for the crop sector included land,<sup>labor, water, machinery (separately for tractor,</sup> thresher, and harvester), draught animals, fertilizer<sup>(separately for nitrogen, phosphorus, and</sup> potash), and pesticide costs (separately for aerial<sup>and ground spray), and for the livestock sector,</sup> labor, fodder and feed, and interest and maintenance<sup>costs (shed, veterinary supplies, and other</sup> cost).<sup>10</sup> The annual use of these inputs for 19 districts<sup>over a period of 1966-94 was estimated.</sup> All stock values were converted to flow values.<sup>Land was evaluated at its rental value, and</sup> family labor at its opportunity cost of unskilled<sup>labor. Labor stocks were multiplied by a year-</sup> and gender-specific participation rate (number<sup>of days labor used in agriculture in a year), based</sup> on household survey data collected annually by<sup>the Punjab Economic Research Institute (PERI).</sup> Similarly, machinery service price include interest<sup>and depreciation on capital, and operation</sup> cost which includes labor, fuel, shed and maintenance<sup>costs based on annual utilization rates.</sup> Changes in the quality of conventional inputs are<sup>often confounded with changes in TFP (Alston,</sup> Norton, and Pardey, 1995). To avoid this problem<sup>i) labor was disaggregated into skilled and</sup> unskilled labor based on the rural literacy rate<sup>in each district; ii) land was divided into irrigated</sup> and unirrigated land; and iii) water into canal and<sup>tubewell water. The price of each input-quality</sup> type were separately estimated based on annual<sup>surveys by PERI. This high level of</sup> disaggregation resulted in a much richer data set<sup>than previously employed for analysis of</sup> productivity trends in the Punjab.

> 9 District boundaries define these systems reasonably<sup>well. In three of the systems there is one dominant crop</sup> rotation. Only in the wheat-mixed system is there a<sup>much variation in crop rotation. In the wheat-mungbean</sup> system the majority of the land is fallowed in the summer<sup>season due to water scarcity. See Byerlee and Hussain</sup> (1992) for details.

> 10 Depreciation cost was not included in livestock<sup>as appreciation of the younger stock was assumed to cancel the</sup> depreciation of older stock.

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