In 1997, non-households sent 84 percent of First-Class Mail, up from 77 percent in 1990.
More First-Class Mail was sent by non-households in 1990 than in 1997. 
mnli hypothesis: More First-Class Mail was sent by non-households in 1990 than in 1997.  premise: In 1997, non-households sent 84 percent of First-Class Mail, up from 77 percent in 1990.