Read the rest:A day laborer waiting on a street corner for a morning's worth of work hacking brush. A sweatshop employer paying less than minimum wage and skimping on overtime. A woman running a day care center out of her apartment. Drug dealers, sex workers, unlicensed street food vendors. A plumber who deals only in cash or a farmer who trades food for help with the harvest.What do they all have in common? They're part of the "shadow economy." Also known as: the underground economy. Pick an adjective, any adjective: informal, gray, black market, under-the-table, hidden, unobserved. There are many different names for the realm where taxes aren't paid, labor laws are ignored, and cash is king. But on at least one point most observers agree: the shadow economy -- in the U.S. and abroad -- is growing. And that's not healthy. In a shadow economy, workers are often unsafe and ruthlessly exploited, while governments are deprived of crucial revenue -- yet still forced to foot the bill for essential services.
http://www.salon.com/news/politics/feature/2011/09/29/shadowintro/index.html