Health insurance costs are about to go up. Maybe way up.

For those of you who have private health insurance — insurance provided by your employer, for example — prices are going to rise about 10% on average, based on initial data from states.

But if Congress does not act fairly soon, insurance rates will rise a lot more for the 13 million Americans who get insurance through the Affordable Care Act marketplace, and 1 million Americans will face health insurance costs that are double what they pay today.

This is a little complex but so important,...