The U.S. is experiencing one of the worst droughts in recent history. While the farm sector directly accounts for only about 1% of the U.S. economy, the hit to farm output is likely to be large enough to have a noticeable impact on U.S. GDP. We estimate that a sharp drop in farm inventories as a direct result of the drought will shave just over ½ percentage point from GDP growth in the second half of this year. This effect will be quickly reversed early next year. Furthermore, a rise in the price of food late this year and into next year will lower real income and wealth enough to shave an additional one-tenth from GDP growth in the fourth quarter of this year and the first quarter of next year, with this effect gradually reversing as prices return to baseline. In this Macro Musing, we discuss how we arrived at these estimates.
Project 2012 NIPA farm value added using USDA projections. The U.S. Department of Agriculture (USDA) prepares detailed projections of several measures related to farm income. Included in the details are receipts from sales of crops and livestock, purchases of inputs, interest expenses, spending on contract and hired labor, etc. BEA uses these data to estimate value added in the farm sector. While it’s not possible to reproduce BEA figures with precision — some of the data are unpublished, and BEA makes some adjustments — we can arrive at reasonable estimates. USDA’s August 28 detailed projection of 2012 farm income and related measures suggests nominal value added in the farm sector of $133.5 billion for 2012, down 3.7% from 2011.
Fill in Q3 and Q4 2012 farm value added given 2012 projection and published values for Q1 and Q2. Using BEA’s published estimate of nominal farm value added for the first half of this year, we judgmentally filled in values for the third and fourth quarters to hit the 2012 annual total. This resulted in a 17% annualized decline in nominal farm value added from the first half of 2012 to the second half.
Project farm prices using USDA reports. Implicit in USDA’s projection for 2012 receipts from farm sales are projected prices for crops and livestock. From various USDA reports, we compiled forecasts for prices of corn, soybeans, wheat, cattle, hogs, and milk. Historically, variation in these prices has accounted for the majority of variation in overall farm prices. We used these projections to generate a forecast of the price index for NIPA farm value added. From the first to the second half of this year, we project a 26% annualized increase in the price index for farm value added.
Deflate Q3 and Q4 2012 nominal farm value added with the projected NIPA price index to arrive at real farm value added in Q3 and Q4 of 2012. The quarterly profiles we assume for nominal farm value added and the price index in the third and fourth quarters imply that (annualized) real farm value added will decline $14 billion (46% annual rate) in the third quarter and $12 billion (46% annual rate) in the fourth quarter.
Project real farm value added over 2013 and 2014. Over the last 35 years, real farm value added has trended higher at roughly a 3% annual rate. Chart 1 shows the log of real farm value added along with this trend over history and in our forecast. Notice that farm output dropped sharply from 2010 to 2011, reflecting drought conditions last year. Our projection for real farm value added shows recovery over 2012 and 2013 that reverses not only the effects of this year’s drought, but last year’s drought, too.

A quick aside on GDP, value added, and spending. Nominal GDP is the sum of value added across all producing sectors of the economy. It is also the sum of final sales and inventory investment across all goods and services, regardless of the producing sector. Any change on the value-added side, therefore, must be matched in magnitude by a change on the spending side. A drop in nominal farm value added, in particular, holding constant value added in other sectors, must be matched by a drop in nominal spending on final goods and services or inventories (or some combination of the two). In real terms, though, this is only approximately true, because real GDP is not additive across components of real value added or across components of real final sales and inventory investment. A change in real value added in one producing sector, holding constant real value added in the other producing sectors, need not be matched exactly by a drop in real final sales or inventories. But the correspondence usually will be close.
Estimate the response of farm inventories to the decline in real farm value added. We assume that the direct hit to real farm value added is reflected on the spending side in farm inventory investment only.3 Furthermore, rather than assuming that the hit to real farm value added is absorbed exactly by farm inventory investment, we estimate the response of farm inventory investment using our error-correction model that links real farm inventories to real farm value added. This allows for the possibility of an effect on the spending side (in real farm inventory investment) that is different from the direct effect on real farm value added.4 Finally, we judgmentally adjusted down the prediction of our model for farm inventory investment over the second half of this year by an average amount equal to 1½ standard errors of the model. We did this to move the estimated hit to real farm inventory investment close to our estimate of the hit to real farm value added.
In our forecast, real farm inventories decline at an annual rate of $14 billion in the third quarter and $30 billion in the fourth quarter. (See the section of Table 1 titled “Forecast Including Direct Impact of Drought.”) This would follow declines in the first and second quarters averaging about $2½ billion per quarter. Were it not for the drought, our model of farm inventories would have predicted a $2 billion annualized increase in farm inventories in the third quarter and a $4 billion increase in the fourth quarter. (See the section of Table 1 titled “No 2012 Drought Baseline.”) The difference between the drought and no-drought projection for the level of farm inventory investment in the third and fourth quarters is $16 billion and $34 billion, respectively (Table 1, “Direct Impact of Drought”). The difference between the drought and no-drought projection for the change in farm inventory investment in the third and fourth quarters is $16 billion and $17 billion, respectively, implying subtractions from GDP growth in the third and fourth quarters of 0.6 percentage point per quarter (relative to the no-drought baseline). This is our estimate of the direct hit to GDP growth from the drought.
Early next year, as conditions are assumed to return to normal, real farm value added rises quickly (see Chart 1) and real farm inventory investment rises rapidly. The contribution to GDP growth in the first quarter of next year is nine-tenths, and the contribution in the second quarter is five-tenths. The level of real farm inventory investment rises above baseline to begin rebuilding depleted farm inventories.
Estimate the indirect effect of higher food prices. While prices received by farmers are expected to rise substantially from the first to the second half of this year, retail prices for food are expected to rise considerably less. This is because raw materials (grain and livestock) account for only a small share of the cost of finished foods. Other costs include processing, packaging, transportation, advertising, retail margins, and so on. In late August, the USDA projected that the CPI-U for food at home, on a year-over-year basis, would rise from 2.5% to 3.5% in 2012 and 3.0% to 4.0% in 2013. We filled in a reasonable monthly profile for the CPI-U for food at home that hits the middle points of these ranges to generate Chart 2, which shows the 12-month percent change in the CPI-U for food at home as projected by USDA (including the effects of the drought) and, for reference, the 12-month change that would result were the CPI-U for food at home to rise from August forward at the rate it has risen on average over the last 20 years (0.22% per month).
Using a relative importance of 0.07, which is roughly the nominal share of food and beverages purchased for off premises consumption in total PCE, we estimated the boost to annualized quarterly growth of the PCE price index implicit in the difference between growth of the CPI-U for food at home in USDA’s forecast and the no-drought alternative. That boost is about 0.1 percentage point in the third quarter of this year, 0.4 percentage point in the fourth quarter, and 0.2 percentage point in the first quarter of next year. (See the section of Table 1 titled “Indirect Impact of Drought from Higher Food Prices.”) After that, the boost turns into a subtraction of one- to two-tenths over several quarters (as prices return to baseline). We simulated the effects of this boost to the PCE price index using our macroeconometric model and found that GDP growth was reduced by one-tenth in the fourth quarter of this year and by one-tenth in the first quarter of next year. The contribution to GDP growth rounds to zero over the balance of next year. Combining this with the direct impact of the drought, we estimate that annualized GDP growth will be reduced by six-tenths in the third quarter and by seven tenths in the fourth quarter (Table 1, section “Total Impact of Drought”). During the first half of next year, assuming conditions return to normal, GDP growth will be boosted by an average of seven-tenths per quarter.
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