In today’s edition of The New York Times, Stephen S. Roach, Chairman of Morgan Stanley Asia, suggests that a weak dollar policy would cure America’s current economic challenges. He calls for tilting the U.S. economy “toward exports” and suggests that such a policy “will require export-friendly measures like a weaker dollar.” Mr. Roach could not be farther off the proverbial mark.

Dollar depreciation is no substitute for enhanced competitiveness. Indeed, such an approach can yield higher inflation and reduced productivity. Initially, dollar depreciation would lower the price of U.S. goods and services relative to foreign alternatives on the world markets. That would translate into higher prices for U.S. consumers and increased revenue for U.S. exporters. However, that revenue advantage would be temporary.

Such a “free lunch” for U.S. exporters is not viable over the longer-run. With such companies porking up from increased revenue achieved solely through changed currency values, those businesses might well develop a disincentive for making the productivity-enhancing investments necessary to flourish in a demanding international marketplace. After all, why make such investments with uncertain returns and opportunity costs when lower currency values could yield similar benefits and seemingly at no cost?

In reality, there is no “free lunch” when it comes to foreign trade. If a nation wishes to achieve an improved trade balance, a better approach would lead to its businesses making the capital, human resources, and best practices investments necessary to achieve and sustain sizable gains in productivity. Only then could such companies have a chance to achieve enduring competitive advantages over their foreign competitors.

Lower corporate tax rates, reduced capital gains taxes, and a stronger dollar resulting from a combination of fiscal discipline and sound monetary policy would provide such firms with a powerful incentive to invest in productivity. Such an economic environment would leave more capital available for private enterprise and at lower long-term interest rates, make it worthwhile for more people or organizations to invest in U.S. companies, and encourage such companies to deploy those resources toward building decisive competitive advantages. Moreover, it would do so without breeding growth stifling inflation.

In sum, Mr. Roach’s strategy amounts to little more than protectionism through currency manipulation. It seeks to “protect” U.S. companies from the need to innovate and improve by administering the bad prescription of a still weaker dollar. That is nothing less than economic malpractice.

Mr. Roach’s bad medicine is not a new prescription. Former Treasury Secretary Robert Rubin debunked that approach more than a decade ago. He explained that the key to reducing a nation’s trade deficit rests with its improving its competitiveness, not depreciating its currency. In short, Rubin explained, if a nation seeks the virtuous combination of “low inflation, low interest rates and a strong economy, a piece of that is the strong dollar.”