21.   Not only will the number of Americans double within the next century, he said, but immigration will add to population pressures.

22.   Social worker Kerouane estimates that the number will double in just two years.

23.   That number has doubled since the attacks.

24.   That number will probably double this year.

25.   That number now doubles as my Medicare ID, and Medicare, of course, vigorously logs all my late-life illnesses and infirmities.

26.   That number could double as the site gets off the ground and starts updating stories throughout the day.

27.   That number doubled in the second year, and continued to grow steadily.

28.   The number has doubled in the last four years.

29.   The numbers double by the end of high school.

30.   The number doubles for out-of-town fans who stay overnight in Seattle.