NEW YORK — The nation's retailers had a rough 2008, but this year will likely be even scarier, according to a sales forecast released today from the world's largest retail trade organization.

Retailers are expected to record a 0.5 percent drop in revenue in 2009, the first annual decline in three decades and perhaps much longer, according to a National Retail Federation forecast released today.

That's well below the modest 1.4 percent gain they recorded for 2008.

Massive layoffs, slumping home prices and tight credit are keeping shoppers tightfisted.

The NRF estimated that retail sales for the first half of 2009 will fall 2.5 percent. Then, they'll show a 1.1 percent decline in the third quarter and a 3.6 percent increase in the fourth quarter, aided by an anticipated stimulus.

Another factor that should help sales figures for late 2009 is that sales were so dismal in the fourth quarter of 2008 — declining 1.7 percent, according to Rosalind Wells, NRF's chief economist.

For November and December combined, sales fell 2.8 percent.