It grew from 5.2 billion pieces in 1987 to 9.9 billion pieces in 1997.
the number of pieces grew in a linear fashion, as opposed to an exponential one.
mnli hypothesis: the number of pieces grew in a linear fashion, as opposed to an exponential one. premise: It grew from 5.2 billion pieces in 1987 to 9.9 billion pieces in 1997.