As everyone who has read "The Grapes of Wrath" knows, the last time we had a major national economic crisis, back in the 1930s, thousands of out-of-work Americans poured into California hoping for jobs picking crops. But in today's recession, California farmers can't find enough workers bring in the harvest - even though the state's unemployment rate tops 10 per cent, the third-highest in the nation. A recent survey by the California Farm Bureau Federation found that nearly two out of three growers are short of workers, despite raising the wages they offer. One-fifth of them said they've cut back on planting or left crops unharvested as a result.

You can't wholly blame the unemployed for turning up their noses at picking tomatoes: farm work is famously hard and low-paid. The federal Agriculture Department's latest survey says field workers are earning a little over $10 an hour these days; activists say that when you factor in the seasonal nature of the work, over the course of a year the average farmworker family basically earns about the poverty level. That's why, as the big growers freely admit, they rely heavily on illegal immigrants. But with a worker shortage this dire, those wages should rise, or so Economics 101 would have us believe. So where is the invisible hand of the market when you need it?