In the second half of 2008, the IRS increased the standard mileage rate to 58.5 cents per mile from 50.5 cents per mile for people who use their personal car for business use. This was in response to skyrocketing gas prices earlier in the year.

Since then, gas prices have dropped dramatically. Prices were as high as $4.10 in some states during the summertime, but have dropped to a national average of $1.90 in this last week in November.

I was wondering how the IRS...