Doug Campbell writes,

Schneider in 2003 published “shadow economy” estimates (defined broadly as all market-based, legal production of goods and services deliberately concealed from the authorities) for countries including: Zimbabwe, estimated at a whopping 63.2 percent of GDP, Thailand’s at 54.1 percent, and Bolivia’s at 68.3 percent. Among former Soviet bloc nations, Georgia led the way with a 68 percent of GDP shadow economy, and together those nations had an average 40.1 percent of GDP underground. This contrasts with an average of 16.7 percent among Western nations.

Thanks to Tax Policy Blog for the pointer.
For Discussion. Does organized crime thrive more in countries with large underground economies?