Many well-meaning commentators look back on the era of strong private-sector unions and robust U.S. trade surpluses with longing. The Progressive consensus (articulated by Robert Reich, among others) is that unions gave the working and middle classes bargaining power that has been lost in the decline of unions.

Other commentators look back with similar nostalgia on the large trade surpluses (i.e. current account surplus) of the same era--the 1950s and 1960s.

The two trends are connected. Unions had bargaining power because the corporations on the other side of the table were generally cartels (autos, steel, etc.) that were largely domestic, meaning that they were captive to domestic markets and politics.

All these conditions have changed. Present-day U.S. corporations are global, not domestic; up to 75% of their sales and/or profits are generated in overseas markets, and a similar percentage of their workforces are also overseas, not just for cost reasons but to stay close to the markets generating their profits.

Free-trade agreements restrict attempts to protect domestic markets from overseas competition, and as a result domestic unions have essentially zero bargaining power with either nominally American firms or their global competitors in most markets. The only sectors open to union bargaining power are domestic monopolies or cartels with no overseas competition, i.e. the government, which is why the union movement is now dominated by public unions.

The trade surpluses vanished for two reasons: global competition and to protect the dollar as the world's reserve currency. This is a difficult issue to grasp, so let's do it in parts:

1. When the global exporting nations recovered after World War II, their costs of labor and production were cheaper than American industry, which was hobbled by the strong dollar. For example, $1 bought 250 yen as recently as the early 1970s. Today, it barely buys 100 yen.

2. As a result, cheap imports took market share from domestic producers (believe it or not, BMWs were once relatively cheap), and the U.S. trade balance went negative, i.e. the U.S. ran trade deficits. To settle the deficits, the U.S. had to ship gold to the creditor nations.

3. As the trade deficits expanded, America's gold holdings shrank. The writing was on the wall: continued deficits would eventually shrink the U.S. gold holdings to zero, at which point deficits would be impossible to sustain.

4. As a result, President Nixon closed the gold window and the U.S. dollar floated in a market of supply and demand.

The second half of the story is Triffin's Paradox, an issue I have covered in depth:

What Will Benefit from Global Recession? The U.S. Dollar (October 9, 2012)

Understanding the "Exorbitant Privilege" of the U.S. Dollar (November 19, 2012)

Prior to 1971, the dollar was backed by gold, which acted as a supra-national anchor to the dollar's reserve status. The gold standard inhibited both massive trade deficits and money creation, so it was jettisoned.

The Triffin paradox is a theory that when a national currency also serves as an international reserve currency, there could be conflicts of interest between short-term domestic and long-term international economic objectives. This dilemma was first identified by Belgian-American economist Robert Triffin in the 1960s, who pointed out that the country whose currency foreign nations wish to hold (the global reserve currency) must be willing to supply the world with an extra supply of its currency to fulfill world demand for this 'reserve' currency (foreign exchange reserves) and thus cause a trade deficit. (emphasis added)

The use of a national currency (i.e. the U.S. dollar) as global reserve currency leads to a tension between national monetary policy and global monetary policy. This is reflected in fundamental imbalances in the balance of payments, specifically the current account: some goals require an overall flow of dollars out of the United States, while others require an overall flow of dollars in to the United States. Net currency inflows and outflows cannot both happen at once.

In other words, the U.S. must "export" U.S. dollars by running a trade deficit to supply the world with dollars to hold as reserves and to use to pay debt denominated in dollars. Other nations need U.S. dollars in reserve to back their own credit creation.

It is impossible for the U.S. to maintain the reserve currency and run trade surpluses. It's Hobson's Choice: if you run trade surpluses, you cannot supply the global economy with the currency flows it needs for trade, reserves, payment of debt denominated in the reserve currency and credit expansion.

If you don't possess the reserve currency, you can't print money and have it accepted as payment. (The euro and yen are quasi-reserve currencies based on the size of the European Union and Japanese economies, but neither acts as the primary reserve and as a result both are vulnerable to currency crises, despite the conventional wisdom that both are on the same footing as the U.S. dollar.)

Unions have little bargaining power in a global economy with surplus labor and mobile capital, and trade surpluses are impossible for the nation possessing the reserve currency. Some view this as a liability, but any currency that is not the reserve currency is vulnerable to a currency/credit crisis and collapse, for currency and credit are tied at the hip through reserves.

Those who disbelieve that the yuan, yen and euro are vulnerable to currency/credit crises--please check in around September 2015.

My new book The Nearly Free University and The Emerging Economy (Kindle eBook) is available at a 20% discount ($7.95, list $9.95) this week.