A survey of employers results in a top 5 worker shortages by trade, and STEM accounts for 4 of the 5: http://finance.yahoo.com/news/help-most-wanted-5-biggest-100000155.html

What's interesting to me is the lack of understanding these employers seem to be displaying regarding supply and demand, because a common complaint in the article is that employers are being turned down because the candidates want more money. If a skill is harder to find, you can expect to pay more for it.