This number is wildly over inflated. Also, one of the ways that they come up with wildly over inflated numbers and try to justify them as real is as follows.
Any person who goes without health insurance coverage for 1 day counts as "uninsured."
So, if you change jobs and your health insurance coverage between employer A and employer B has a gap of 1 day, you are considered uninsured.
Note the numbers: they say 45 million people are uninsured. This number is wildly over inflated.
You are correct. Regardless, the number as a percentage of the overall population has remained relatively constant for the last 20 years or so.