One recurrent theme among the many New Year prognosticators is that of sustainability. While this theme is obviously appropriate in discussions of environmental concerns, its applicability to economics isn’t necessarily as immediately clear. But consider sustainability—

—in energy. T. Boone Pickens has done the United States a service by demonstrating the economic unsustainability of current energy usage patterns. While everybody certainly has the right to use (and waste) energy if they can afford to, consider the boost for the domestic economy from reduced imports of crude oil, replaced by renewable energy sources or those domestically available, such as nuclear power or natural gas. Narrowing the trade gap can only strengthen the economy at a fundamental and sustainable level.

—in consumerism. The U.S. consumer cannot support the entire planet and manufacturers in emerging economies must base their anticipated growth elsewhere while households in the States retrench and pay off loans. The current ratio of household debt to after-tax income stands at 139% and in 2007, consumer spending was fully 70% of U.S. gross domestic product, above the historical average of 66%. While four percent may not sound like much, that’s an estimated $550 billion of spending per year, much of it enabled by credit rather than income.

Central banks, including the Federal Reserve and the Bank of England, regularly survey loan officers, and the results of these surveys show that credit remains tight and may tighten further. Many households in developed economies (not only the U.S.) will therefore have no choice but to continue deleveraging before going on another spending spree, reducing debt-income ratios and levels of consumer spending to sustainable levels.

—in real estate. All markets, including housing, should be driven by demand, not by investors or builders. So-called “house flippers” who purchase residential real estate, slap on a coat of paint and plant a few shrubs, then resell within months, do little for the market beyond driving up prices. In the most heavily overbuilt and overpriced areas of the nation, such as Florida, California, Arizona, and Nevada, these short-term investors accounted for as much as 33% of the prime loans in default and 25% of the subprime ones, pushing the first round of foreclosures in those areas. (The second round is being driven by fundamental factors such as lost employment.)

Even more telling is the regional ratio between the average monthly mortgage payment and the average monthly income. In Houston, one of the most residentially affordable metropolitan areas in the nation, this ratio is 16.6; however, in Reno it’s 30.2, in Miami it’s 46.8, and in Los Angeles it’s 63.5. Such levels are not sustainable and it’s possible housing prices in these areas have further to fall.

—in financial markets, including currencies and commodities. This is too obvious to require discussion. The most egregious examples are crude oil at $150 per barrel and the yen trading at such high levels against the U.S. dollar that Toyota registers its first operating loss in 70 years and the market invites intervention by the Bank of Japan.

The overindulgences of the U.S. economy are best summarized by the single term consumer. Beloved of economists and widely utilized (mea culpa) for its simplicity and clarity, it nevertheless reduces people to a biological and need-driven level rather than a human or reasoning one; after all, bacteria are consumers, too.

Perhaps its all-too-common usage by economists and the media has convinced us that consumption is the true meaning of our financial existence. Perhaps the change most needed by the U.S. economy isn’t in political parties or governmental administrations. Perhaps it’s in our view of ourselves.