After giving up some gains in May, the Accountants Confidence Index plummeted in June.

The ACI, published in partnership with ADP, is a monthly economic indicator that leverages the insights of accountants into the strength and prospects of businesses in the U.S. The 3-Month ACI dropped to 44.24, down from the previous month's 55.31 -- and well below the 50 mark that represents expectations of contraction. The 6-Month ACI, meanwhile, came in at 50.62, down from last month's 57.64, but still just barely in growth territory.

It was by far the biggest drop since the ACI began in 2011, but it mirrored drops in other major economic indicators, such as the Consumer Confidence Index, and may well reflect concerns about uncertainty in Washington, and the Trump administration's difficulties getting tax reform and the repeal and replacement of the Affordable Care Act off the ground.

The ACI is created from a monthly poll of the Accounting Today Executive Research Council, an online community of more than 1,500 tax and accounting professionals.