Why did my health insurance go up so much? Often, it's because you had a birthday.

We often hear from consumers who say that their rate increase was substantially higher than what we approved.

One of Washington's major health insurers, for example, recently increased its premiums for individual plans an average of 13.5 percent. The highest increase among the plans was 21.5 percent. But we subsequently heard from consumers who are seeing rate hikes of 35 percent or more.

What's going on? Birthdays.

If you had a birthday in the past year and your new age ends in a zero or a five (55, 60, etc.), then you can expect a rate increase when your individual health plan renews. This is because you moved into a higher age band. (The insurers group ages together, five years at a time.) Since medical costs tend to increase with age, your premiums tend to jump every time you move to the next five-year band.

And when an age band increase combines with an across-the-board rate increase for everyone who’s on the health plan, you get a sort of double-whammy: the total rate increase can be substantially higher than what our agency approved.