I've read a lot of literature on the topic that seems to like doing one of two things to determine this number:
1. using the results of a 1986 paper and adjusting dollar figures based on 2006 dollars.
2. using the current average hourly salary data for the area.
The first idea seems stupid to me...case closed.
The second seems like specious reasoning at best that would far over-estimate the typical person's wage (how about housewives? and old people? is their time worth $16.00/hr? or is their time worthless because it's not paid time?) I could include some measure of the labor force participation rate (but have seen no one else do this)...but surely a housewife's time is worth something if not as high as the average of an employed person. ...and how 'bouts the all important opportunity cost?
Let's get serious...is the area wage rate a reasonable gauge for how much an hour of the average person's (employed or not employed) time is worth?