11.   In medicine, costs are driven by factors like new technology and the aging of the population that are terribly difficult to control.

12.   Librarians and booksellers say that as mighty as Harry is, there is no doubt that other factors are also driving the fantasy book boom.

13.   Many factors are driving the increase in homes with multiple PCs, including the growing availability of powerful computers that are more affordable.

14.   Other factors may be driving the phenomenon, too.

15.   Several factors are driving the proposals by New York, California and other states.

16.   Several factors are driving the upswing in immigrant deaths, Border Patrol officials agree.

17.   Several factors drove Saleaumua back to school.

18.   Several factors are driving accounting firms to venture into new arenas.

19.   Several factors are driving the upswing in migrant deaths, Border Patrol officials agree.

20.   Several factors drive this trend.