A collapse in trade. Millions thrown out of work. Sterling tumbling on the markets, and the government phoning up the IMF to ask for an emergency bailout. There are plenty of scare stories out there about what might happen to the U.K. economy if the country votes to leave the European Union in the upcoming referendum.

And yet, in reality, investors should ignore the hype. A so-called Brexit won’t actually make much difference to the economy one way or another.

The EU has no incentive to put up trade barriers against the U.K., and global companies will still invest in the country. On the other side of the ledger, the U.K. won’t suddenly be turned into a free-wheeling, free market offshore island — a sort of Singapore, with added drizzle. EU membership makes a difference politically, but the economy and the stock market will sail on with the same strengths and weaknesses as before.

When the Queen’s Speech sets out the legislative program for David Cameron’s re-elected Conservative government today, by far the most important item will be the vote on whether the U.K. will stay in the EU. Cameron has pledged to renegotiate the terms of British membership, and then put the question to the people.

The Economic Debate Over Trade Authorization

It will be a close-fought contest. At the last European elections, the fiercely anti-EU U.K. Independence Party topped the polls. Opposing a referendum hurt the Labour Party at the election earlier this month. A substantial part of the electorate clearly thinks that Britain would be better off out.

That said, the polls at the moment equally clearly show a majority in favor of staying. Even so, there will be plenty to play for. A poll this month for The Times showed 34% of people would definitely vote to stay in, while 18% are certain to vote to leave, with 34% of the electorate saying they could be persuaded one way or the other.

The impact on the economy will be crucial in making that choice. In the run-up to the vote, there will be plenty of warnings about the dire impact quitting the EU might have on the economy. Indeed, it has already started. Deutsche Bank DBK, -1.40% has already warned it might leave the City of London if the U.K. left the Union. So have companies such as Siemens SIE, -1.17% , Airbus AIR, -3.27% , and the Japanese car manufacturers with big plants in Britain such as Nissan 7201, +1.31% and Honda 7267, +0.88% .

Pro-EU political leaders such as the former Prime Minister Tony Blair and the former Deputy PM Nick Clegg are fond of quoting a study that claimed 3 million jobs would be lost in the event of a Brexit.

On the other side of the argument, UKIP and the anti-EU campaigners argue that outside of the EU Britain would be liberated from the tide of regulations that come out of Brussels. It would be free to deregulate its labor markets, abandon expensive energy policies, control immigration, join free trade agreements with other regions, and import cheap food from anywhere in the world. Liberated from the shackles of EU membership, and the influence of an increasingly protectionist France and Germany, it could grow a lot more quickly.

And yet, neither case is really very strong. On close examination, the claims of both camps don’t stand up to much scrutiny.

Although Europe remains the U.K.’s largest export market, no one can seriously believe trade will suffer if it quits the EU. Tariffs and trade restrictions are governed by the World Trade Organization, and since Germany is the third biggest exporter in the world (selling only slightly less stuff around the world than the U.S., despite being far smaller) it is hard to imagine that country is going to start breaking the global trade rules by banning British exports. It would destroy its economy if it did.

Keep in mind as well that the U.K. runs a massive trade deficit with the rest of Europe, so they have far more to lose in any kind of trade battle than the U.K. does, and it is clear there won’t be any less access to the European market. Nor is it really the case that fewer companies will invest in the U.K. They come to the country because it is a big market, they know the language, and it has a stable legal system, flexible labor markets, and lower corporate taxes than most other European countries.

None of that will change. The U.K. will still be an attractive place to base a business.

The benefits of getting out don’t amount to much either. True, the U.K. will no longer be subject to employment, energy and regulatory laws made in Brussels. But it has plenty of meddlesome bureaucrats and free-spending politicians of its own, who will replace rules made in Brussels with regulations written in Whitehall.

Britain is a mature, developed economy, with a long social democratic tradition. It isn’t suddenly about to turn into a lightly regulated emerging market. Outside the EU, it will have more freedom to agree trade deals with other regions — it might well join the North American Free Trade Agreement (if they swap the American for Atlantic). But it will lose the ability to shape EU laws for its own advantage, which may hurt the City. The net result? Again, it won’t make much difference.

We will find out soon enough whether the vote is to be held next year or in 2017. We will also find out whether France and Germany are willing to offer Cameron the kind of concessions that would keep the U.K. inside the club, or have already concluded that the British are such reluctant members that the EU it might be better off without them.

A lot will depend on whether Cameron himself decides to recommend a yes or no vote. Until then, there will be lots of scare stores about the impact on sterling GBPUSD, +0.25% , on the City, and on the U.K. stock market UKX, -0.70% .

But in reality, the economy will carry on much as before regardless of whether the U.K. stays in the EU or not.