Every year the government adjusts the SNAP (or food stamp) program's numbers to account for cost of living increases. Found a really good resource that shows you all the changes per year, since 2004, and it's updated every year so it's always current:
Cost of Living Adjustment (COLA) Information
Changes include new income eligibility standards, different deductions and different minimum and maximum allotments. Per the site:
We adjust SNAP maximum allotments, deductions, and income eligibility standards at the beginning of each Federal fiscal year. The changes are based on changes in the cost of living. COLAs take effect on October 1 each year.
Maximum allotments are calculated from the cost of a market basket based on the Thrifty Food Plan for a family of four, priced in June that year. The maximum allotments for households larger and smaller than four persons are determined using formulas that account for economies of scale. Smaller households get slightly more per person than the four-person household. Larger households get slightly less.
Income eligibility standards are set by law. Gross monthly income limits are set at 130 percent of the poverty level for the household size. Net monthly income limits are set at 100 percent of poverty.
So if you're looking for a good place to see the yearly changes to SNAP, bookmark this one.