City government experts point to a political culture that's been in place for more than 100 years, in Chicago. This culture dates back to the late 19 ^th   century, when a gambling-house owner named Michael Cassius McDonald created the city's first political machine. Under machine-style rule, those in power would hand out contracts, jobs, and social services in exchange for political support.

Chicago's large immigrant population made it easier for political machines to grow in power. Poor ethnic communities could be played off against one another and manipulated with petty gifts. In exchange for political support, ethnicities would be given virtual fiefdoms within city government; the Irish, for example, were given police work, and the Italians jobs at the transit authority.

Of course, none of this was unique to Chicago. New York City had large immigrant populations and the notorious political machine at Tammany Hall. But machine politics faded away in New York, due in part to external pressure from former New Yorker, Franklin Delano Roosevelt (FDR), who was elected president in 1932.

In Chicago, corruption persisted, to some degree because the city never had the benefit of a reformist mayor like New York City's Fiorello LaGuardia, who had political ties to FDR. Instead, Chicago moved towards a one-party system that made it even more vulnerable to corruption. Today, not even the Democratic primaries are competitive − for the most part, once you're in office, you stay there.

The star power of Chicago politicians may also contribute to the city's continuing problems with corruption. Incumbents tend to be big personalities who get celebrity coverage in the local papers − which sometimes translate into ethical flexibility from voters.

How do we know that Chicago's so corrupt? The most straightforward way to measure corruption is to check the number of convicted local officials. Between 1995 and 2004, 469 politicians from the federal district of Northern Illinois were found guilty of corruption. The only districts with higher tallies were central California (which includes L.A.), and southern Florida (which includes Miami). Eastern Louisiana (and New Orleans) rank somewhat further down the list.

But a high conviction count doesn't necessarily mean more corruption. It could mean that a district happens to have very strict transparency laws or a zealous and effective federal prosecutor—like Patrick Fitzgerald in Chicago. You might try to measure corruption by checking the number of city employees per 1,000 people. Or you could check to see how long it takes to acquire a construction permit through legal means.

Public perception may be the most useful measure. If the inhabitants of a city view corruption as given, they'll be more inclined to forgive politicians who have already been tainted by scandal, like Chicago's current mayor, Richard Daley.