These Are the Most Vermin-Filled Cities in the U.S.(BusinessWeek)

Roach motels, mouse traps, and rat nests

Tampa, Fla., is among the roachiest big cities in America. Seattle may be the rattiest. Philadelphia has more mouse sightings per housing unit than any other U.S. city. These are some of the filthy highlights from the U.S. Census Bureau's biennial accounting of rat, mouse, and cockroach sightings across the country. The most recent numbers, collected in 2013, were released last month.

The data comes from the American Housing Survey, which is conducted every two years. And it does have limitations. For one, the survey includes only households, so sightings in public areas like subways and sidewalks don't count. And in each installment, the Census breaks down detailed data for only 25 metropolitan areas. This year, the list included Chicago, Houston, and New York—but it didn't include Dallas, Los Angeles, or San Francisco.

Which means that while Richmond, Va., had the smallest share of households that reported signs of a rat among the 2013 cohort, it isn't necessarily the U.S. city with the fewest rats.

It's apparent from the data that the variety and quantity of vermin is at least partly determined by geographical factors. Mice were more likely to be found in colder, Northern cities. Roaches and rats seem to reproduce more rapidly in warmer climates.

So what cities appear to be the most and least infested overall? We ranked each city from 1 to 25 for each type of pest, with lower numbers meaning that sightings were less common. New York, allegedly the city of 2 million rats, had the highest cumulative score. (Austin was second.) Detroit ranked as the city where residents are least likely to report a mouse, rat, or cockroach—somewhat surprising given the blighted condition of the city's housing stock.

Despite its limitations, the data offers some insights into quality of housing and quality of life—and perhaps into the effectiveness of local public health efforts. The National Center for Healthy Housing links exposure to rodents and cockroaches to asthma and other health risks. In Boston, city officials have linked improved pest control to a sharp drop in asthma symptoms among public housing residents.

Compared with the national average, households living below the poverty line were 50 percent more likely to report evidence of rats or roaches. Black and Hispanic households were also far more likely to report those two categories of pests. Houses and apartments built in the last four years were far less likely to be visited by vermin.

Mice, however, were reported evenly across demographic lines. Squeak.