Government shutdowns have been around for 40 years, 5 of them happened in the past 13 years

Benjamin Civiletti was a U.S. Attorney General who issued two opinions in 1980 stating that federal government agencies cannot remain open if they are not funded. It means non-essential services shut down, and that essential workers may not be paid - that's the case with TSA workers.

Before that, there were funding gaps but no shutdowns.

SEE ALSO: To avoid long TSA lines during shutdowns, some experts believe airports could privatize screening

It is a controversial decision. Government oversight agencies, including the Government Accountability Office, have disputed Civiletti's narrow view of the 19th-century law. But the Supreme Court has never struck down those opinions that framed how our government operates without funding.

Before 1980, there were just six funding gaps - but no shutdowns. It wasn't until Civitelli's opinion in 1980 that agencies were found to be unable to operate without funding.

Since then, there have been 12 shutdowns, five of them since 2013.

The shortest lasted a day. The longest, at the end of last year, lasted 43 days. Though the current partial shutdown will likely break that record.

The United States is essentially the only country whose government shuts down without funding in place.

In Europe, they either call for new parliamentary elections and vote in new representatives who will vote to fund the government before they run out of money, or use what's called an automatic funding measure that keeps funding at the previous budget level until a new one is approved. Congress could do that, but has not.

As for the history of shutdowns, if it seems like it's happening more than ever, that's not really the case.

Four decades ago, there were eight funding gaps during the Reagan administration. And of those eight, four resulted in shutdowns.

Reagan served two terms, so there was an average annual funding gap.

More recently, there have been five shutdowns since 2013. There was a shutdown under the Obama administration in 2013. That's when Republicans controlled the House and Democrats controlled the Senate. This was in the first year of President Obama's second term.

Under President Donald Trump's two terms, there have been four shutdowns so far. That includes the partial shutdown happening now. In all four, Republicans controlled both the House and the Senate.

Passing a funding bill in the House requires a simple majority, but in the Senate, it takes 60 votes. There are 53 Republicans, so they need some Democratic support to pass a funding bill. And that's the sticking point - Democrats don't want more funding until they get changes to the Trump administration's immigration enforcement policy.

READ MORE: Trump says he's 'pretty much not happy' with any deal to reopen DHS as negotiations continue

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