You may think spin-doctoring and economics are worlds apart, but they combine in that relatively modern invention the "free-trade agreement" – the granddaddy of which, the Trans-Pacific Partnership , is presently receiving CPR from the lips of our own heroic lifesaver, Malcolm Turnbull.

It's not surprising many punters assume something called a "free-trade agreement" must be a Good Thing. Economists have been preaching the virtues of free trade ever since David Ricardo discovered the magic of "comparative advantage" in 1815.

Many people oppose free-trade deals on the grounds that ordinary workers end up worse off. Andrew Harrer

Nor is it surprising the governments that put much work into negotiating free-trade agreements – and the business lobbyists who use them to win concessions for their industry clients – want us to believe they'll do wonders for "jobs and growth".

What is surprising is that so many economists – even the otherwise-smart The Economist magazine - assume something called a free-trade agreement is a cause they should be supporting.

Prime Minister Malcolm Turnbull and Japan's leader Shinzo Abe said the TPP would foster investment, generate billions in export revenue and create thousands of jobs. AAP

Why's that surprising? Because you can't make something virtuous just by giving it a holy name. When you look behind the spin doctors' label you find "free trade" is covering up a lot of special deals that may or may not be good for the economy.

This is the conclusion I draw from the paper, What Do Trade Agreements Really Do? by a leading US expert on trade and globalisation, Professor Dani Rodrik, of Harvard, written for America's National Bureau of Economic Research.

Rodrik quotes a survey of 37 leading American economists, in which almost all agreed that freer trade was better than protection against imports, and were in equal agreement that the North American Free-Trade Agreement (NAFTA) to eliminate tariff (import duty) barriers between the United States, Canada and Mexico, begun in 1994, had left US citizens better off on average.

Their strong support for freer trade is no surprise. One of the economics profession's greatest contributions to human wellbeing is its demonstration that protection leaves us worse off, even though common sense tells us the reverse.

And that, just as we all benefit from specialising in a particular occupation we're good at, then exchanging goods and services with people in other specialties, so further "gains from trade" can be reaped by extending specialisation and exchange beyond our borders to producers in other countries.

Winners and (more) losers?

What surprised and appalled Rodrik was the economists' equal certainty that NAFTA – a 2000-page document with numerous exceptions and qualifications negotiated between three countries and their business lobby groups – had been a great success.

He says recent research suggests the deal "produced minute net efficiency gains for the US economy while severely depressing wages of those groups and communities most directly affected by Mexican competition".

So there's a huge gap between what economic theory tells us about the benefits of free trade and the consequences of highly flawed, politically compromised deals between a few countries.

Trade agreements are the result of rent-seeking, self-interested behaviour on the part of politically well-connected firms. Professor Dani Rodrik, Harvard

Rodrik says trade agreements, like free trade itself, create winners and losers. How can economists be so certain the gains to the winners far exceed the losses to the losers - and that the winners have compensated the losers?

He thinks economists automatically support trade agreements because they assume such deals are about reducing protection and making trade freer, which must be a good thing overall.

What many economists don't realise is that the international battle to eliminate tariffs and import quotas has largely been won (though less so for the agricultural products of interest to our farmers).

This means so-called free-trade agreements are much more about issues that aren't the focus of economists' simple trade theory: "regulatory standards, health and safety rules, investment, banking and finance, intellectual property, labour, the environment and many other subjects besides".

International agreements in such new areas produce economic consequences that are far more ambiguous than is the case of lowering traditional border barriers, Rodrik says, naming four components of agreements that are worrying.

First, intellectual property. Since the early 1990s, the US has been pushing for its laws protecting patents, copyrights and trademarks to be copied and policed by other governments (including ours). The US just happens to be a huge exporter of intellectual property – in the form of pharmaceuticals, software, hardware, music, movies and much else.

Tighter policing of US IP monopoly restrictions pits rich countries against poor countries. And though free trade is supposed to benefit both sides, with IP the rich countries' gains are largely the poor countries' losses. (Rich Australia, however, is a huge net importer of IP).

Second, restrictions on a country's ability to manage cross-border capital flows. The US, which has world-dominating financial markets, always pushes for unrestricted inflows and outflows of financial capital, even though a string of financial crises have convinced economists it's a good thing for less-developed economies to retain some controls.

Third, "investor-state dispute settlement procedures". These were first developed to protect US multinationals from having their businesses expropriated by tin-pot governments.

Now, however, they allow foreign investors – but not local investors – to sue host governments in special arbitration tribunals and seek damages for regulatory, tax and other policy changes merely because those changes reduced their profits.

How, exactly, is this good for economic efficiency, jobs and growth?

Finally, harmonisation of regulations. Here the notion is that ensuring countries have the same regulations governing protection of the environment, working conditions, food, health and safety, and so forth makes it easier for foreign investment and trade to grow.

Trouble is, there's no natural benchmark that allows us to judge whether the regulatory standard you're harmonising with – probably America's - is inadequate, excessive or protectionist.

Rodrik concludes that "trade agreements are the result of rent-seeking, self-interested behaviour on the part of politically well-connected firms – international banks, pharmaceutical companies, multinational firms" (not to mention our farm lobby).

They may result in greater mutually beneficial trade, but they're just as likely to redistribute income from the poor to the rich under the guise of "freer trade".