Online holiday spending will rise 16 percent to more than $61 billion this season, reflecting stronger economic optimism among consumers, market researcher ComScore Inc. projected.

E-commerce spending in November and December on desktop personal computers will reach $53.2 billion, a 14 percent gain from a year earlier, ComScore said Tuesday in a statement. Mobile shopping is forecast to jump 25 percent to $7.87 billion, accounting for 13 percent of total holiday e-commerce.

The spending gains are being fueled by improved consumer sentiment, with the stock market near record highs and mild inflation, according to ComScore. An extra shopping day between Thanksgiving and Christmas this year is also benefiting retailers, said Adam Lella, an analyst at ComScore.

“We are seeing healthy growth,” Lella said. “We expect mobile to grow at a faster rate going forward, but it won’t be split even, since it’s just an easier experience to shop on the desktop.”