Supermarket sales in 2009 dropped to a 21-year low of ¥12.83 trillion amid the anemic economy, the Japan Chain Stores Association said Friday.

Sales for the January-December period, down 4.3 percent on a same-store basis, sank below the ¥13 trillion threshold for the first time since 1988, the association said.

The number represented the 13th consecutive year-on-year drop on a same-store basis.

"Consumers tightened their purse strings in 2009 because their disposable incomes shrank, deepening their anxieties over the outlook of the economy," the association said.

This tendency led supermarket operators to cut back on the unit prices of commodities, it said.