In July, research and consulting firm Corporate Insight presented an impressive number: $15.7 billion.

That was the amount of money managed by the online investment platforms known as robo-advisers.

By once again analyzing 11 leaders in the field this December, Corporate Insight has determined that since its last analysis, these robo-advisers have taken more than another $3 billion under management for a total of nearly $19 billion.

This number represents a 21% increase since July, and a 65% increase since the first time the data was collected in April.

"The continued growth of the newcomers and the recent actions of the major players prove that online advice is not a fleeting fad," Corporate Insight analyst Grant Easterbrook wrote in an email to Business Insider. "Human advisers must realize that the disruptive powers of the web and automation are here to stay."

Corporate Insight looked at the influence of online platforms Wealthfront, Betterment, Assetbuilder, Covester, Financial Guard, FutureAdvisor, Jemstep, MarketRiders, Personal Capital, RebalanceIRA, and SigFig.

Easterbrook says the innovative new partnerships and products announced by Fidelity, TD Ameritrade, TradeKing, and Charles Schwab, as well as the $161 million raised in funding rounds by four of these 11 robo-advisers this year, is clear evidence that robo-advice is being welcomed into the mainstream.

The growth, segmented into "discretionary control" (money that's directly managed) and "paid investment advice," is shown in the chart below:

See Also:

The Sony Hackers Pranked The FBIYoung People Are Risky Investors And It Isn't Paying OffRobo-Advisers Now Manage 21% More Money Than They Did 5 Months Ago

SEE ALSO: Here's Why Betterment's CEO Loves That People Call His Investing Website A 'Robo-Adviser'