A kerfuffle was stirred up last week by a devastating McKinsey & Company study that concluded up to 78 million Americans would lose their current health coverage as employers stopped offering insurance because of President Obama's Patient Protection and Affordable Care Act.

The report contradicted Mr. Obama's frequent pledge that under his reform, "if you like your health care plan, you can keep your health-care plan." And McKinsey's was at least the fourth such analysis calling the president's promise into question.

In May 2010, former Congressional Budget Office (CBO) Director Douglas Holtz-Eakin concluded that employers would drop coverage for about 35 million Americans because of ObamaCare. A month later, in June 2010, the National Center for Policy Analysis (NCPA) pegged the number between 87 million to 117 million. And last November, Allisa Meade, a McKinsey analyst, told health insurance company executives that 80 million to 100 million people might lose their employer-provided health insurance.

Simple economics is the reason. According to the Kaiser Family Foundation's Employer Health Benefits 2010 Annual Survey, the annual premium for an average policy last year was $5,049 for a single worker, with the company picking up roughly $4,150 and the employee the rest. For a family of four, the total cost was $13,770, with the company picking up $9,773.

Yet under ObamaCare, businesses can stop providing health care coverage, paying a $2,000 per-worker fine instead. For small businesses, the trade-off is even more attractive: They are given a pass on the first 50 workers.

Karl Rove is a former senior adviser and deputy chief of staff to President George W. Bush. He is a Fox News contributor and author of "Courage and Consequence" (Threshold Editions, 2010). To continue reading his column in The Wall Street Journal, click here.

Karl Rove joined Fox News Channel as a political contributor in February 2008. He also currently serves as a columnist for the Wall Street Journal. Mr. Rove helped organize the political-action committee American Crossroads. His latest book is "The Triumph of William McKinley: Why the Election of 1896 Still Matters" (Simon & Schuster, 2015). Follow him on Twitter @KarlRove.