Hello- I have not done a full comparison yet, but there are a couple of things that I have flagged in my mind...
The first is that the employer industry distribution does not match that of the United States. For example, less than 1% of Truven's population (2008 to 2013) is in "construction, agriculture, forestry, and fishing." But in the United States ~8.2% of the employed population with employer-sponsored health benefits is in the construction sector. I've attached part of a table I'm working on now that shows more of what I'm talking about.
Second, since Truven only includes large firms, it does not represent employees in small/medium sized firms. I do not have great numbers to compare yet but at least 50% of the US population works in the small/medium sized firms and 50% of employees at these firms have employer sponsored health insurance. So that's a chunk that's missing.
I appreciate you and @schuemie's responses.