Bank of America Corp.‘s second quarter earnings released yesterday make clear this: mobile banking is it.

According to the megabank’s second quarter earnings, the share of customers moving to mobile is significant. This reaffirms the numbers released last week by JPMorgan Chase and Wells Fargo.

(Citigroup, in typical laggard fashion, doesn’t release data for online and mobile users.)

Specifically, BofA’s mobile banking user base grew more than 28% last quarter to 13.2 million compared to the same quarter in 2012. Meanwhile, BofA’s online banking users fell 1.2% to 29.9 million during the same timeframe.

Perhaps more tellingly, the ratio of mobile to online users at all three big banks has jumped substantially:

• BAC 44.2% / +1,021 basis points
• JPM 43.5% / +839 basis points
• WFC 47.1% / +780 basis points

We look at those numbers and see the gears turning away from online to mobile. If this isn’t happening at your bank yet, it will — BofA, Wells and JPM are leading indicators. These numbers should explain why Chase’s retail banking advertising campaign today is centered on mobile banking.

The doubters are going to run the numbers and point out that at the current pace, mobile banking will overtake online banking at Bank of America, for example, in around six years. My response would be twofold: a) six years isn’t that long in the grand scheme of banking; and b) the pace of adoption has accelerated and will continue to accelerate. I’d handicap that milestone at around two to three years at the major banks — and that certainly is not a long time in the grand scheme of banking.