21.   No one tracks the number of doctors performing procedures not covered by insurance or how that number has changed, but there are many indications that it is growing.

22.   Nobody tracks the number of students studying piano in the United States.

23.   No organization or association tracks the number of teachers who loop.

24.   Now Chevron will try to track the number of flu-related absences this winter among its vaccinated and unvaccinated drivers.

25.   Of the local armored-car robberies, an overwhelming number are tracked to Charlestown residents, officials said.

26.   Or that Dollar Rent A Car System tracks the number of times customers rent from them.

27.   PC Data tracked the number of unique home Internet users that came to each site preceding and after the game on Sunday.

28.   Products are shipped from participating shops, but LooknBuy follows up with confirmation e-mails containing shipping information and tracking numbers, much like many U.S. online sites.

29.   Riess-Lane noted that tracking the number of women buying guns is difficult.

30.   Requests are also received at individual prisons, but the numbers are not tracked, she said.