How glum are we Americans? When asked by the NBC NewsWall Street Journal poll how we compared the past 10 years to other decades, 55 percent of respondents answered either “a very bad decade” or “one of the worst decades in American history.”

Mark Shields

Mark Shields

But it was the answer to the very next question in the same survey that explained to me the nation’s current melancholy: “Thinking about the first 10 years of the 21st century, which of these events had the greatest effect on you personally.” The list included the terrorist attacks on Sept. 11, 2001, the U.S. wars in Iraq and Afghanistan, the federal budget deficit, Hurricane Katrina, the BP oil spill in the Gulf and the economic recession.”

Not surprisingly, a full one out of three — 33 percent — named 9/11, the date and events of which have changed our own lives and our nation’s. From the way we travel, work, shop and live, nothing has been the same since that day of terror and death. Another 11 percent answered that their lives had been most influenced by the wars in Iraq and Afghanistan.

But the event of the past decade that has had the greatest impact upon Americans — chosen by two out of five of us (39 percent) has been and continues to be the economic recession.

It is both national and personal. From the end of 1999 all the way to 2010 — while the nation’s population was growing by more than 27 million — there was no net increase in private-sector jobs.

We have lived through a lost decade. Median-income American households made less last year, when adjusted for inflation, than they did 10 years ago. More than 15 million of us are still unemployed this Christmas season, more than 40 percent of whom have now been out of work for more than for six months. Millions more are now classified as “involuntary part-time workers” because their hours have been cut back or they have been unable to find full-time employment.

Employers, even when they do need additional help, have resisted hiring full-time permanent workers. According to The New York Times, after the mild recession at the beginning of the decade, just 7.1 percent of the new workers were temporary hires. But this year, that share of part-time, temporary hires has nearly quadrupled, to 26.1 percent.

Workers, whose own self-confidence and cohesiveness have been frequent casualties to actual layoffs and the corporations’ implicit threat to ship their jobs off-shore, now accept wages and working conditions that, less than a generation ago, would have been unacceptable or even grounds for a strike vote.

Add to all of this the losses of the value — including, sadly, too often the ownership, as well — of Americans’ homes, of their pension and retirement funds, and their investments and savings, and you can understand why Americans’ traditional optimism — the same spirit that settled the frontier and built a national society that has been truly the envy of the world — is today in such perilously short supply.

The iron rule of U.S. politics remains: When the economy is bad, the economy is the only issue; when the economy is good, other issues — as important as saving the environment or as trivial as reciting the Pledge of Allegiance — can gain voters’ attention.

In the winter of 2010-11, in this uncharacteristically gloomy land of ours, the economy is indeed bad. And jobs and the economy remain the only issue!

Mark Shields is one of the most widely recognized political commentators in the United States. The former Washington Post editorial columnist appears regularly on CNN, on public television and on radio. Click here to contact him.