(Bloomberg View) — The next big shift is coming in health care, and Republicans are doing their best to speed it up. What's not clear is how carefully they've thought through the consequences.

A defining feature of health care policy is that most Americans get insurance through their employers. That has frustrated liberals' attempts to rally voters behind Obamacare's modest reforms, let alone the single-payer model that works so well in most developed countries: The average person has no incentive to support changes that might jeopardize their situation.

But judging by the trend of the past few years, Americans with job-based coverage could soon become a minority. The chart below shows the percentage of Americans younger than 65 with health insurance provided by their employer. (Almost everyone 65 and older is covered by Medicare.) There has been a gradual but steady decline, from 59.2 percent in 2009 to 57.1 percent in 2013.