According to a 1998 U.S. Geological Survey study the mean number of economically recoverable oil in the ANWR 1002 area is 5.2 billion barrels (found in the caption of Fig 6 on page 6). Mean technically recoverable oil within the ANWR 1002 area is 7.7 billion barrels (see "Summary" pg 6).

The difference between technically recoverable and economically recoverable is what is physically able to be brought up from under the ground and what can actually be brought up out of the ground within a reasonable level of economic viability.

The Bush administration likes to quote a figure of 10.4 billion barrels, and that number comes from the same "summary" section of the report. However statistically speaking there's only a 5% chance of that much technically recoverable oil being there. That's in the summary section too.

To put this in perspective, in 2002 the United States consumed 19.76 million barrels of oil per day. (See this chart) That works out to about 7.2 billion barrels for the year.

Yet another analysis shows that the absolute peak production that ANWR could potentially ever hit is 1.9 million barrels per day, but that won't happen until 20 to 30 years from now and there's only a 5% chance of it happening at all. (See section 3. Summary) The more likely case is 600,000 barrels per day, in the same time interval.

Just for argument's sake let's split the difference and call peak production 980,000 barrels per day, or 357.7 million per year. That's about 5% of total US oil consumption in the year 2002. In 2020 that consumption is going to be significantly higher, and that production rate might not even be reached until 2030.

All in all we're not talking a hugely significant decrease in the American dependence on foreign oil. It would be far better to reduce total consumption rather than bump domestic production by a few percentage points.