The chairman of the Senate finance committee said up to 25 US companies are considering inversions this year to avoid US taxes.

Sure, this raises questions about tax fairness and gaming the system but that’s old news. The real question is: How does a Senator have so much advance notice on M&A?

“With the investment bankers in that inversion feeding frenzy, there may be 25 more inversions during [this year],” Ron Wyden said.

That’s an odd number to pull out of thin air and Congressional insider trading is a well-known problem.

Robert Stack, a senior official at the US Treasury department, told the hearing: “We are aware of many more inversions in the works right now”.

Some of those may be already-announced deals like Walgreens and Alliance Boots but that doesn’t get the total to 25. I have no confidence that Congress can keep that kind of information out of the hands of traders. Meanwhile, Congress can continue to refuse to provide records of insider deals to investigators.