The Govenment passed a Population Law forbidding anyone from having more than two children. Luke and Jen are third children and therefore they are Among the Hidden. If they are found the government will kill them. The reason the Government passed the Population Law was because it was afraid that it would run out of food if the population kept growing. They were trying to get everyone to become vegetarians because it cost less to grow soybeans than to raise a pound of meat. Luke tells Jen that in the past they fed the grain that the Government found inferior to the pigs. The Government made them get rid of the hogs, so now Luke's father just lets the grain rot in the field.
This information excites Jen and she rushes to the computer where she posts
"If the Government let farmers feed their animals the grain they can't sell, there'd be more meat." (pg 82)
She posted this on the Department of Agricultures bulletiln board in hopes that some Government worker would see it, and the thought might take root in someone's brain.
Jen is a very smart young lady, but she takes a lot of chances. It doesn't hurt that her father is a high ranking official in the Government, and that fact helps Luke in the next book.