A friend directed me to a site on labor market statistics for the areas affected by Katrina. This is issued by the Bureau for Labor Statistics. The data reflect wage data and employment for the "most affected areas", defined as "the 8 counties in Alabama, 31 parishes in Louisiana, and 47 counties in Mississippi that were designated by the Federal Emergency Management Agency (FEMA) for both individual and public disaster assistance as of September 8, 2005." The area contains over 145,000 establishments with about 2% of national employment and about 1.5% of the nation's wage bill. The area had an unemployment rate of 5.8%; it was over 7% in many of the counties and parishes.

By far the flooding in Louisiana did the most damage to the local economy -- 18,000 firms were flooded out, with quarterly wage bills of nearly $3 billion. Most of the damage in Mississippi was due to the high winds of Katrina itself, but the total damage there was about $415 million.

All told, in the most affected areas about $76 billion in wages were paid in 2004. If that area uses labor at about the same rate as the economy as a whole, the hit to GDP as a result of the damage done should be somewhere around 1% of GDP. That's pretty large, but not catastrophic, and still probably unlikely to tip us to recession. James Hamilton's guess that at least 200,000 jobs are lost for several months looks quite reasonable with the data provided by BLS today.