This piece originally published on The Edge Markets.

Banks, your customers are quietly leaving you.

When Bain & Company surveyed 83,000 customers in 22 countries recently, we found that more than one-third of them bought a banking product from their primary bank’s competitors during the past year. The rate of defection reached an average 47% in developing countries. In Malaysia 68% of customers went to a different bank to obtain a credit card, buy insurance, or apply for an auto loan or another financial product.

If that many bank customers were closing their current accounts each year—completely defecting—bankers would be up in arms. Yet the hidden defection, often involving more lucrative products, goes largely unnoticed by banks because they seldom know their customers were shopping in the first place or that they lost the business.

This trend is accelerating as digital startups and specialist firms, less encumbered by creaky old IT systems and a thicket of banking regulations, offer better, simpler solutions and make it easy for people to find them. Strong demand for peer-to-peer lender Lending Club’s recent initial public stock offering is just the latest sign of investors’ and customers’ confidence in alternative business models.

Meanwhile, banks’ classic advantages—personal relationships between bank managers and customers, big branch network and a reputation for security—have been crumbling. Even regulation in some countries, such as the UK, has grown more accommodating, as regulators who once frowned on new business models now want to promote competition.

As a result, bank revenues and profit margins look more and more vulnerable. In Germany, France and Italy, for example, Bain estimates that at least 30% of retail bank revenues are at risk of migrating or disappearing by 2020.

Read the full article at The Edge Markets.

–Written by Maureen Burn and Harshveer Singh, partners in Bain & Company’s Financial Services practice.