This week, an AgWeb reader in Hancock County, Iowa, wrote: "We have obliged with our crop conditions, and that is helpful to all of us. But everyone is asking where USDA comes up with their numbers. Can you obtain any remarks from them? We would all appreciate this."
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In response to that question, AgWeb reached out to Julie Schmidt, agricultural statistician with the National Agricultural Statistics Service (NASS), for more information about how weekly planting progress, crop condition and crop emergence reports are gathered. She shared the following steps:
1. Each week, NASS generates and sends questionnaires to Extension and Farm Service Agency agents in counties throughout the U.S. The survey is sent to about 4,000 people each week. NASS wants every county to be represented in the report, though response rates vary. In some cases, a single county might have multiple reporters, while other counties may not be represented.
NASS strives to cover as many of the agriculturally important areas within a state as possible so that the best representation of a crop is provided. National crops such as corn, soybeans, sunflowers and sugar beets are among those for which planting progress, emergence and crop condition data are gathered, though states can choose to add questions about local crops.
2. County data is compiled into districts and then into a state-level report that is sent to NASS headquarters in Washington, D.C.
3. County data are weighted by NASS County Estimates. NASS tries to include the states that encompass the largest percentage of production for a given crop as part of the National program. These states are weighted using the previous year’s acreage, so that the U.S. estimate is more reflective of planting or crop development progress in the larger-producing states.
For example, of the 18 corn-producing states surveyed, the U.S. estimate would be more heavily influenced by progress in Iowa than by other states because it had the most acreage planted to corn in 2012. Each state’s progress estimate is multiplied by the previous year’s acreage for a given crop. Those products are then summed, and that sum is divided by the sum of the previous year’s acreage for those 18 states.
By incorporating acreage for weighting, the U.S. estimate is more representative of what is happening in the areas where the larger portion of a crop is grown.
"It’s definitely a look at the aggregate," Schmidt says.
She acknowledges that reporting can vary widely, even within a county. A farmer who received plenty of rain one week might live just a few miles down the road from another who hasn’t seen rain in four weeks. The same is true for factors such as crop condition and growth.
"What the numbers try to show is kind of overall, what is going on at the state and the national level as well," Schmidt says.