Much has changed since February, when we published our first list of the healthiest housing markets for 2009.

The federal government’s $8,000 tax credit for first-time home buyers spurred sales around the country. Companies with cash are buying land again. A handful of builders have begun emerging from Chapter 11 bankruptcy.

But the housing downturn surely is not over yet, despite economists’ assertions that statistics will show that the recession ended in June. Home values have fallen dramatically this year, and some believe prices still haven’t hit bottom. In terms of employment (a key factor for home sales), all but three of the top 100 housing markets have lost jobs since we published our February story.

Given these factors, we decided to revisit our list and see how individual markets have fared this year—and where builders need to be in the months to come.

We took advantage of this occasion to improve the metric by which we rank the markets by adding more data to the calculations. Now we’re ranking markets not just by what’s happened with home price appreciation (or depreciation), job growth, household growth, and unemployment. We’re also considering median income growth as well.

“These are the economic factors that are most correlated to strong home sales,” says Jonathan Smoke, director of research for Hanley Wood Market Intelligence, which compiled the rankings for BUILDER Online. “In the best of times, earlier this decade, many markets had high marks on all these factors, making them the perfect markets for home sales.”

Today, as Smoke points out, the reverse is true. In nearly every market, most of the key home building drivers have turned negative. As a result, virtually no market today is truly healthy, though some are faring better than others. For that reason, the recovery, when it comes in earnest, is likely to be more pronounced in the markets that head our list.

Each market on the list received a Market Health Indicator score, with a score of 50 or more considered healthy. Only one market on this list surpassed 50.

To give more builders across the country a sense of where an individual market stands nationally, we’ve expanded the list to include the 100 largest home building markets, ranked by permit volume. Interestingly, many smaller markets showed up on our list of the healthiest, in part because they didn’t have big run-ups in housing appreciation during the boom. Many of them also benefit from more diversified economies than other formerly booming metros.

We’ve also improved the BUILDER Market Health Index to make it timelier and more consistent. We’ve included forecasts, where appropriate, so that all the data, with the exception of building permits, is good through August.

Again, our list should help identify the markets that are likely to recover first from the downturn. Some are already on their way up. In Washington, D.C., for instance, new home sales were up 17% through June, and builders there have been able to pass through some price increases.

If you would like a broader and more detailed ranking of the top 200 markets, you can click on this link to purchase the BUILDER Market Health Report from Hanley Wood Market Intelligence.

Here, in ascending order, are the 20 healthiest housing markets in the country.