Quite a large range in that estimate, and I don't believe it for a second. And I don't believe for a second that there are not adequate numbers of Americans willing to train for good paying jobs. We see the occasional immigration raid on restaurant chains and slaughter houses where hundreds of illegals are removed from jobs, then large numbers of Americans apply for and fill the jobs within no time at all.
17% - 18% real unemployment, yet they can't find qualified trainees for millions of high paying jobs?
But that absurd range from 3 - 15 million unfilled jobs throws the entire claim into question. Some pretty imprecise estimates involved there.
We have too many unskilled people (the brighter ones need to be taught skills) and college graduates who don't want to run a lathe, say, or fix HVAC systems, but not skilled workers.
That can be fixed if the educations system forgets about 'women's studies' and 'black studies', re-emphasizes vocational training.
Too often companies have no interest in training people. They want to hire people for the duration of a project and let them go when they no longer need them. Re-hire again when the demand is there again. That's a tough system for people in that field and tougher for those trying to get in.