NEW YORK (CNN/Money) - Some of the nation's frothiest housing markets are at growing risk of price declines, according to the most recent survey from PMI Mortgage Insurance Corporation.

The PMI Risk Index is based on economic activity and other conditions that PMI thinks are predictive of home-price declines over the next two years.

Factors used to derive the index include home prices, employment conditions and the affordability of homes.

At a 55.3 percent chance, the index singles out Boston as the area most at risk for a decline. That's up from 53.4 percent three months earlier.

The Nassau and Suffolk County area, in suburban New York, is right on Boston's heels. The probability of a decline, according to PMI, is 54 percent, up from 51.1 percent.

The metro area that had the biggest increase in risk is Riverside-San Bernadino, east of Los Angeles, which rose 8.3 points to 42.2 percent.

Some areas got a little safer during the quarter. Among them, Detroit had the biggest drop from 37.9 percent to 29.5 percent while New York's risk score fell from 33.1 percent to 32.6 percent.

So where are homeowners all but guaranteed to not go through a bubble burst?

They can breathe easiest, according to the PMI listing, in Pittsburgh (5.6 percent), Memphis (5.8 percent), and Indianapolis (5.9 percent). Among western cities, Seattle scored the safest, at 6.4 percent.

Here are other cities tracked by PMI, with their probability of a decline during the next two years.