Estimating the economic impact of the Gulf oil spill is a largely speculative exercise at this point. The variables are significant—how much has been spilled and how much more is coming? Where will it come ashore? How long will it take to clean up? The list goes on.

What we do know is that the fishing, recreation, and tourism sectors in the Gulf are already feeling the effects. The extent of the impact depends on the duration of the spill—the longer it continues, the worse the impact. That's a pretty easy call.

Some of the projections are nightmarish. David Kotok of Cumberland Advisors paints a dire picture, writing that "Three scenarios lie ahead. They rank as bad, worse, and ugliest (the latter being catastrophic and unprecedented). There is no 'good' here."

Jonah Goldberg in USA Today suggests that we keep the oil spill in perspective. "But it's worth remembering that the damage from previous, and much larger, spills wasn't nearly so lasting as people had feared."

Nobody is downplaying the event and its impact on the environment, nor should we forget about the 11 people who lost their lives in the tragedy. What we will do going forward is keep up with current events and attempt to measure their potential impact based on confirmed information we gather. Here are some sources of information that we are tracking to keep up to date with the economic impact of the spill.

The U.S. Department of the Interior's Mineral Management Service along with other agencies has created a Web page dedicated to the Gulf of Mexico Oil Spill Response that features regular updates, maps, and fact sheets. You can also register to receive e-mail notification of updates. Here are some others we are tracking:

The White House has a regular blog on the spill as well as containment efforts.

The National Oceanic and Atmospheric Administration is providing coordinated scientific weather and biological response services to federal, state, and local organizations.

The Wall Street Journal is also providing regular updates and coverage.

By Michael Chriszt, assistant vice president in the Atlanta Fed's research department