You might assume that a shutdown of the federal government, which started to take effect Tuesday, would at least save taxpayers some money, even if it meant they couldn’t visit the National Zoo or get someone from the Small Business Administration on the phone. But you’d be wrong, according to the Office of Management and Budget.

The OMB, in a 1996 letter cited in a recent Congressional Research Service report, estimated the cost of the two government shutdowns in late 1995 and early 1996 (26 full days in total) at “over $1.4 billion.” Adjusted for inflation, that’s $2.1 billion in current dollars.

Much of that sum, wrote University of Maryland-Baltimore County political science professor Roy Meyers in 1997, was for back pay granted to furloughed federal workers — in other words, “what the government paid for the outputs it largely did not get on time.” It’s unknown whether federal workers would get any back pay after the government reopened for business  this time around.

But, Meyers continued, simply looking at salaries and other input costs may understate a shutdown’s real impact: “Was the cost to the economy [of delayed economic data from the Bureau of Labor Statistics and the Bureau of Economic Analysis] only the salaries and expenses of collecting this data, or was it greater? Did delayed IRS revenue collections cost more than the bill for paying auditors for taking a long Christmas break? What were the costs to those citizens who had to delay their enrollment for benefits, or to those who changed vacation plans due to closed national parks or unavailable passports?”

Drew DeSilver  is a senior writer at Pew Research Center.