Wal-Mart Stores and Amazon.com helped to boost online shopping during the fourth quarter, researcher ComScore Inc. said.

Online retail spending rose to $39 billion last quarter, a 2.6 percent gain from the year-earlier period, the Reston, Va.-based research company said. More shoppers bought items online, while the average amount spent per person declined, ComScore said.

Retail e-commerce spending totaled $129.8 billion in 2009, less than the previous year’s $130.1 billion. The fourth quarter saw the first increase in online sales since the third quarter of 2008, the research firm said.