NEW YORK (AP) — Amazon is hiring 80,000 seasonal workers for its distribution centers as it looks to improve its shipping efficiency during the crucial holiday season.

The figure is a 14 percent increase over last year's hiring of 70,000 workers, as Amazon has been opening more distribution centers.

It now has more than 50 distribution centers in the U.S., up from 40 last year. And in July it announced it was opening eight smaller sorting centers for a total of 15 by year-end. At the centers packages are sorted by ZIP code and then transported to U.S. Postal Service offices.

The company says the sorting centers help Amazon offer services such as Sunday delivery, a later cutoff order time and tighter control over shipping logistics.

Thousands of the seasonal jobs are expected to become permanent positions.

The pace of hiring at a retailer can serve as an indicator of expectations for the holiday shopping season, which accounts for 20 percent of the industry's annual sales, according to the National Retail Federation, a trade group.

Seattle-based Amazon is hoping to avoid problems that occurred late in the holiday season last year, when shippers such as UPS were caught off guard by spiking online orders, particularly from Amazon.com.

Overall, the National Retail Federation said it expects sales during the November and December period to increase 4.1 percent to $616.9 billion, up a percentage point higher than last year. It marks the highest increase since 2011 when the rise was 4.8 percent.

Amazon employs more than 132,600 full-time and part-time employees globally.