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Number Cruncher Keeps an Eye on Vegetable Supply


Americans ate 4.4 pounds of sweet potatoes per capita last year, and Shannon Hamm is the one who figured it out.

As the U.S. Department of Agriculture's premiere vegetable-number cruncher, it's Hamm's job to calculate not only how many sweet potatoes we each ate, but how many white potatoes, plus 10 other fresh vegetables, five vegetables grown for processing, dried peas and lentils.

"I would love to do beans," she adds.

A graduate of Virginia Tech, the 28-year-old co-ordinator of vegetables for USDA's Economic Research Service started out studying animals (pre-veterinary) but switched to agricultural economics.

"Now I do vegetables. They're much more exciting," she says.

So while farmers across the nation are planting and harvesting, and as consumers shop for side dishes, Hamm sits in a Washington office building, tabulating their every move.

Take those sweet potatoes. To arrive at 4.4 pounds per capita, Hamm first had to determine supply: a total of domestic production (numbers supplied by another branch of USDA), imports (supplied by the Census Bureau) and canned stock (provided by the National Food Processors Assn.).

Then she had to count the potatoes that disappear before they reach the supermarket, such as those that are exported (none, in the case of sweet potatoes), canned inventories being stored by processors and those being used for seed or feed.

Subtract that total from the supply, and you get the amount available to be eaten. Divide it by the U.S. population, and that's per-capita consumption.

Nutritionists use per-capita consumption numbers to calculate the adequacy of the food supply; farmers use them to help figure out which vegetables have been growing in popularity; and canners use them to anticipate demand and supply. Congress may use them to set import and trade policies.

Per-capita consumption figures are also helpful for spotting eating trends. In 1965 per-capita consumption of sweet potatoes was 6.6 pounds. Hamm attributes the 33% decline, in part, to shoppers' looking for more convenient and unusual vegetables. (Demand for white potatoes, however, is up in the last five years, primarily for French-fry exports to Japan.)

Other statistics are as far away as Hamm's computer screen, a government report on the bookshelf or a scan through the agricultural tidbits she stores in her head.

State with the largest sweet-potato production? North Carolina, by far. Country with the largest production? China. And what about yams? Hamm doesn't concern herself with them. Those sweet potato look-a-likes are an entirely different plant and are not grown in this country.

For true collectors of sweet-potato trivia, Hamm digs up some demographic data, as reported by the Packer newspaper in 1988. The study revealed that the typical sweet-potato eater is more likely to be a Southerner older than 60 with a college education and a household income more than $30,000.

Hamm dispenses all this information with an unequalled enthusiasm toward tubers.

"I could tell you what the average annual growth rate is," she exclaims, explaining how since 1970, California has increased its sweet-potato production at a greater rate than any other state. With calculator in hand, she quickly computes California's sweet-potato growth: a 3.4% annual average increase in production since 1970, compared to about 1% for North Carolina.

But Hamm is not just a walking data base. She also coordinates USDA's quarterly "Vegetable Situation and Outlook Report," has written articles such as one on the effect on the food-service industry of iceberg-lettuce production, analyzes price, supply and demand information and answers a virtual vegetal hotline from her office.

An importer from the Dominican Republic wants to know the "market window" for a vegetable he wants to ship to the United States; a Michigan farmer wants to know in what month the domestic supply of melons is the lowest; the Food and Drug Administration wants to know the impact its detention of canned mushrooms from the People's Republic of China will have on U.S. prices and supply.

And her friends kept asking her about Alar, a growth regulator for apples that caused a big controversy last March. "But I don't do fruits," she told them.

There are also other questions she can't answer, like the per-capita consumption of green peppers, or spinach, cucumbers, watermelon and garlic.

"We used to track 21 fresh vegetables," she says, lamenting the effect budget cuts have on the government's record-keeping of fresh produce.

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