What age groupings were represented, and what percent did each age
group represent of the total number of single people who traveled for
leisure purposes in 2001?

Mimart --

Here's where you'd want to go to get the EXACT answer that you're
seeking:
The Travel Industry Association has a "Domestic Travel Market Report"
prepared each year covering business travel, single travel and a
variety of other segments. The 2001 report is $250 for non-TIA
members; the 2002 report is $275:
http://www.tia.org/Pubs/pubs.asp?PublicationID=94

TIA also did a report titled "Travel Profile: Singles, Couples,
Parents & Roommates" that you may find interesting.  It was done in
July, 1999

There is some data available on the web for 1999.  There's also ample
Census data on the percentage of the population that's widowed,
divorced, separated and never married.  It could be used to make some
estimates by age.

A final note: you may wish to clarify "single people" traveling for
leisure.  One study that I saw notes that many married people traveled
alone in the past three years.

Best regards,

Omnivorous-GA