US online ad spending will post growth well above 20% again this year to reach nearly $40 billion, eMarketer estimates, as the internet continues to prove its worth to advertisers in a tough economic climate.

“Advertisers’ comfort level with integrated marketing is greater than ever, and this is helping more advertisers—and more large brands—put a greater share of dollars online,” said David Hallerman, eMarketer principal analyst.

Double-digit growth is expected through 2014, when US online ad spending will reach $52.8 billion. In 2016, eMarketer expects advertisers to spend $62 billion online.