LOS ANGELES: Although summer has barely ended, nearly one-third of US consumers – and nearly half of parents – already started their holiday shopping before Labor Day, a new survey has found.

According to the second annual Holiday Consumer Pulse Poll from Rubicon Project, Americans plan to spend an average of $1,175 this holiday season, a 12% increase on last year.

Much of this double-digit growth is being driven by millennials, who intend to spend an average of $1,427 this year, an impressive 33% increase on the $1,072 they spent in 2015.

Based on a survey of more than 1,000 US consumers conducted at the end of August, Rubicon Project said that a full 39% of millennials have already made a start with their holiday shopping.

Around three-quarters (76%) of millennials say they will shop online and 58% say they will carry out their holiday shopping on their mobile device.

Among all respondents, 73% plan to shop online this holiday season with about a third doing so via mobile. Interestingly, 22% of all shoppers (and 28% of millennials) do not plan to shop in-store at all this year.

Parents, many of whom of course are also millennials, constitute another key segment and the survey indicated they plan to spend an average of $1,711 this year, compared with $1,383 in 2015.

They are also more likely to make purchase decisions online (76%) and on their mobile devices (56%) than other consumers. What's more, American parents plan to spend $495 per child this holiday season, up 25% from $397 last year.

"With Americans shopping earlier and spending considerably more this year than last, retailers have a unique opportunity to target shoppers across a variety of media and platforms," said Harry Patz, Chief Revenue Officer at Rubicon Project.

"The research shows that parents and millennials in particular will be two key drivers behind this year's increase in holiday spend."

Elsewhere, the survey revealed that Cyber Monday (47%) has a slight edge over Black Friday (42%) in terms of shopping intentions.

And even though Cyber Monday doesn't take place until the end of November, the survey found that 22% of American shoppers already started researching Cyber Monday deals back in August.

Data sourced from Rubicon Project; additional content by Warc staff