Booking trends and new studies show that fewer business travelers are tacking on vacation time to a work-related trip. Business travelers are also more concerned about the negative perceptions some have about travel perks, according to Peter Yesawich of the travel research and marketing firm Ypartnership. In 2000, 60% of business travelers said they added a bit of vacation on to a business trip in the past year. In May, roughly 30% said they've combined such trips. Yesawich expects that figure has declined further.