Let's see. According to the US Dep't of Transportation, the average commute in the US in 1995 (old data, I know, but the most current I could find) is 11.6 miles. 11.6 miles at 55 mph = 12.6 minute commute. 11.6 miles at 70mph = 9.9 minute commute. minutes.
Is that two minutes and forty-five seconds each way *really* destroying the economy? I doubt it.
Oh - source for the USDOT info is here.
The average United States driver travels 29 miles per day and is driving a total of 55 minutes per day. (This is an average vehicle speed of 32 mph.) US Department of Transportation, Bureau of Transportation Statistics