The decidedly unsexy bond market is usually pretty quiet. But when they want to, bond investors can send a loud, clear message to Washington. They did just that Wednesday and Thursday.

The bond market has a sleepy reputation, but it can pack a punch when alarmed. And worries are now growing about tax cuts pushed by Washington and how they'll inflate the U.S. government's debt.

Yields on government debt have risen as Congress weighs Trump’s budget plan. Meanwhile, interest on the debt is approaching $1 trillion a year – on par with proposed Defense spending.