President Barack Obama and Congress have until March 27 to reach a budget agreement to avert a government shutdown. If they don’t meet the deadline, federal agencies will halt many public services and send “non-excepted” workers home without pay. Let’s look at some of the misconceptions about what happens when the U.S. government officially closes shop.

1. It won’t happen this time.

The country has weathered several federal shutdowns over the years, and it could happen again. The last threatened shutdown was in 2011; it was narrowly avoided late on Friday, April 8, within an hour of the midnight deadline.

The longest shutdown in U.S. history, which also happens to be the most recent, occurred during Bill Clinton’s presidency and lasted 21 days, from Dec. 15, 1995, until Jan. 6, 1996. It came only a month after a five-day shutdown from Nov. 13 to 19, 1995. From fiscal year 1981 through 1995, during the Reagan, George H.W. Bush and Clinton presidencies, there were nine shutdowns, none lasting longer than three full days. Six shutdowns occurred during Jimmy Carter’s presidency, between fiscal year 1977 and fiscal year 1980, ranging from eight to 17 full days.

This week, the Senate will vote on an amended House bill to keep the government funded. The bill will then go back to the House. But this Congress and this White House have been locked in stalemates too many times for us to feel certain that we’ll avoid a shutdown: Think of the summer 2011 debt-ceiling fight, this year’s sequester showdown and a near-certain battle over the debt limit coming up again this spring. With House Republicans and the Obama administration constantly at odds, why would we think any agreement between them would be inevitable?

2. Shutdowns have little impact on the general public.

Even during a government shutdown, many federal services would be available to the public. Self-funded agencies, such as the Postal Service, would stay open. Uniformed military personnel would stay on the job. And federal guidelines mandate that certain other services continue, including national security functions such as airport screening and border and coast patrol; customs inspections and air-traffic control; and some benefit payments and contractual obligations, such as borrowing and tax collecting (yes, you would still have to pay your taxes).

But there are plenty of other services that would be missing: Citizens couldn’t get or renew passports, and foreign visitors wouldn’t be issued visas, affecting our tourism economy; all of our national parks would close their gates; and the Centers for Disease Control and Prevention would stop monitoring diseases. Veterans would still receive health benefits, but those going through the application process would have to wait even longer to be granted benefits.

During the shutdowns in the 1990s, vital programs took hits. At the end of 1995, 2,400 workers stopped cleaning up toxic waste at 609 Superfund sites, investigations of delinquent child-support payments stopped, and decisions on whether to allow new medical drugs on the market were interrupted. Eleven states and the District of Columbia suspended unemployment assistance for lack of federal funds.

Payments to federal contractors were delayed, something that can be devastating to small businesses. Exports were also affected: Some companies were unable to ship goods overseas because no one was there to inspect them.

3. Shutdowns save money.

It seems counterintuitive, but shutdowns do not necessarily save the government money. Preparing for a shutdown takes time and resources that could be spent delivering services, and any savings that are achieved are minimal compared with the size of the federal budget. In fact, shutdowns can actually cost the taxpayer, because even though furloughed workers are not working, the government traditionally pays them retroactively. The Office of Management and Budget estimated the cost of the shutdowns in 1995 and 1996 at $1.4 billion.

During the two shutdowns in the 1996 fiscal year, the government closed 368 national parks, turning away 7 million visitors; local communities lost that tourism revenue. At the same time, $3.7 billion of a total $18 billion in Washington area contracts were delayed or canceled. The halt in processing visa applications for up to 30,000 foreigners resulted in millions of dollars in losses for the tourist industry and airlines.

A lengthy shutdown, coupled with the sequester, would probably hurt, not help, economic growth.

4. Federal workers lose pay.

Some might, but not if past experience is a guide.

The president, presidential appointees, members of Congress and some career executive branch personnel are required to continue working during a shutdown. They would be paid.

Most federal employees, however, are subject to furlough and not entitled to pay. This includes rank-and-file workers as well as senior leadership. For example, a veterans benefits customer-service representative may have to stay home, as could the division’s managers, if those functions are deemed “nonessential.” (Furloughed employees continue to be credited for benefits and seniority.)

But even though furloughed workers are not legally entitled to pay, Congress has traditionally passed legislation after the fact to compensate them.

5. Shutdowns show that there are a lot of nonessential government workers.

During the November 1995 shutdown, the federal government furloughed 800,000 “nonessential” employees. Hundreds of thousands of workers were furloughed during the December 1995 shutdown, too. If we can do without those employees during a shutdown, why can’t we get rid of them entirely?

It turns out that the government’s narrow definitions of “essential” and “nonessential” don’t always match the common-sense meanings. As Treasury’s assistant secretary of management, George Munoz, testified to Congress in 1995: “These are inappropriate terms that mistakenly convey a sense of relative importance among federal employees. They perpetuate the false impression that some federal workers perform jobs that are trivial or unnecessary.”

Now, the federal government tends to use the terms “excepted” and “non-excepted” to get away from the notion that the vast ranks of feds are “nonessential.” Executive branch employees deemed excepted are required to work during a shutdown because, for example, they perform emergency services involving life or property, or they are involved in the orderly suspension of agency operations. Excepted personnel may include a National Zoo worker responsible for feeding animals, while a zoo employee who manages programming may be non-excepted. An Army information manager may be deemed non-excepted, but an agency budget officer may be considered essential because her job involves ensuring that funding lapses don’t result in overspending.

These bureaucratic terms — excepted and non-excepted — don’t make much sense to the public if a needed service can’t be delivered because the government has shut down. In those cases, pretty much everyone is considered essential.

Blair is president and chief executive of the National Academy of Public Administration, an independent nonprofit chartered by Congress. He served as deputy director of the Office of Personnel Management from 2002 to 2006.