Estimating the Value of California Wine Grapes

The California Grape Crush Report (Crush Report) is an authoritative source of information on production and returns per ton by variety of wine grapes that includes summaries of quantities produced and estimates of the average prices and value of wine grapes crushed in California. The data provided in the Crush Report are used to calculate the total value of wine grape production as reported in the annual Agricultural Statistics reports published by the U.S. Department of Agriculture and in major industry publications. We use the differences among crush districts in the shares of production crushed to growers' accounts to show that the current mechanism of calculating average statewide returns per ton understates the true total value of the crush by 14 to 20 percent. We show that a more accurate estimate of the total value and average price can be obtained if the prices of the wine grapes that are sold are used to infer the prices of wine grapes that are not sold before computing the weighted averages.