This morning, I published an article for the investor-focused website Seeking Alpha, in which I analyzed the most recent annual reports of the 30 companies in the DOW 30 index. While the White House estimated that "Tax Inversions [are] costing Americans nearly $20 billion over the next ten years", my analysis of only 30 public companies shows that they, alone, have "deferred" (and many intend to defer "indefinitely") US taxes on over $630 billion in foreign earnings that are invested overseas. At the current repatriation tax rate of 35%, that would have produced over $220.5 billion in tax revenue. Meanwhile, it also gives companies a big incentive to invest foreign profits overseas instead of in the US--making the tax-adjusted cost of US labor less competitive and costing US jobs.
The full article (link) also shows how this problem is not limited to the DOW 30, and one commenter pointed out that just Apple (not a DOW 30 component) has over $50 billion in foreign earnings that have not been subject to US taxes.