This year the number will quadruple to 24 million shipments.
The number of these towers has quadrupled in three years, according to industry figures.
Between 1972 and 2008, the number of tax expenditures more than quadrupled from 60 to 247.
The following day, a handful of people came through, but yesterday that number had quadrupled.
Within eighteen months there were 190 girls, the number of staff had quadrupled and the school was full.
"Over the last two or three years I would guess the number has quadrupled."
But over the last 15 years, the number of people waiting for organs has more than quadrupled, to 82,000.
Yet the number of Federal and state prison inmates has quadrupled since 1973.
Since then, the number of stations carrying the show has more than quadrupled.
After only 20 years, in 1970 this number quadrupled to 2,065 residents.