Labor Day is upon us once more. As predictably as Americans regret the end of summer, union leaders are using the holiday to trumpet their importance, with T-shirt slogans such as “Kicking Ass for the Working Class.”

The American Federation of Labor and Congress of Industrial Organization’s Web site features “Union 101,” a course so crammed with skillfully-worded myths that it should be entitled “Mythology 101.” The first myth is that unions represent labor. According to Union 101, “a wider range of people than ever before, including many women and immigrants, is joining unions.”

This myth fits in with the long-held assumption of politicians, journalists, and conference planners that organized labor represents the voice and views of American workers. When representatives of workers are needed to give speeches, participate on panels, or testify to Congress, union officials are almost always invited. In fact, unions represent a small and shrinking proportion of American workers. Only 12% of all workers and 7% of private sector workers belonged to a union in 2006, down from 12.5% in 2005 and 20% in 1980, and down far more from a historic high in the 1950s. Between 80% and 90% of workers in traditionally unionized industries, such as manufacturing and construction, do not now belong to unions.

Industries considered part of the “new economy” have little union representation. Just 2% of workers in financial activities and in professional and business services are unionized. One of the more union-heavy sectors — transportation and utilities — can claim only 23% unionization.

Even at their 1950s peak, unions represented only 33% of workers. Then, union membership was concentrated in the Northeast and Midwest manufacturing states. Organized labor was never the “national” movement its supporters claim.

A second myth is that unions work for their members. Union 101 asserts, “Unions are continuing the fight today to improve life for all working families in America.”

But data from new Labor Department financial disclosure forms show that a significant portion of unions’ funds is spent on activities that have nothing to do with improving members’ welfare. Some union bosses are spending members’ dues in three areas that are not directly related to members’ welfare: political activity, leadership salaries, and entertainment expenses.

The AFL-CIO’s president, John Sweeney, admits as much when he says “we are training hundreds of union activists to agitate, educate and mobilize thousands of members beginning with the primary election cycle in 2008 and continuing throughout the year.”

In the 2006 elections, the AFL-CIO spent $40 million on get-out-the-vote efforts, $5 million more than in 2004. And expenditures by political action committees of the top 10 unions — ranked by spending — totaled more than $16 million, according to federal campaign finance data. Political spending by the top 10 union “527 committees” exceeded $38 million.

Political spending data and exit polls show that unions make large contributions to Democratic candidates, whereas many members vote Republican. Over the past 15 years, while unions have on average given 92% of donations to Democrats, between 25% and 40% of members have still pulled the election lever for the Republicans.

Some of the recipients of union support would surprise union members. Union financial disclosure forms revealed that in 2006 unions gave $359,442 to Reverend Jesse Jackson’s Rainbow/Push Coalition. Several of these contributions were quite large, including $150,000 from the Service Employees International Union.

While labor unions often boast, as does Union 101, of their ability “to improve life for all working families in America,” the wages of rank-and-file members often pale in comparison to salaries of union leaders. According to the Census Bureau, approximately 20% of households have incomes above $97,032 and 5% are above $174,012. Union financial disclosure forms show that almost all top union officials fall into these top categories. While some union leaders invoke class warfare rhetoric to appeal to their members, many are in the same income groups that they are criticizing.

For example, among the top 50 paid union officials in 2006 were president of the Food and Commercial Workers Local Union 1288, Don Hunsucker, who made $679,949; and international president of the State County and Municipal Employees AFL-CIO National Headquarters, Gerald McEntee, who made $629,291.

The disclosure forms also make clear that unions spend members’ money on extravagant events that are unnecessary for the functioning of a union. A computer search for golf-related expenses discloses dozens of outings and tournaments, most held at luxurious resorts and courses. For example, Carpenters Local 6 paid almost $19,000 for a golf outing at New Jersey’s Crystal Springs Golf Resort.

A third myth is that unions produce economic benefits for their members. According to Union 101, “Through unions, workers win better wages, benefits and a voice on the job — and good union jobs mean stronger communities.”

Unfortunately, after unionization many employees realize that supposed benefits are mirages. Higher wages often come at the expense of lower demand for workers, that is, fewer jobs. Just compare Alabama’s 3.7% unemployment rate with Michigan’s 7.2%. Detroit’s 7.7% rate is the highest of any metropolitan area.

Professors John DiNardo of the University of Michigan and David Lee of Columbia University analyzed company data between 1984 and 1999 and found that unionization increased unemployment. Deregulation and free trade have reduced unions’ ability to sustain higher wages in our competitive international environment.

Sometimes even the raises that employees might receive through unionization turn out to be a net negative after union dues and fees are subtracted from paychecks. On other occasions, unions successfully organize a workplace only to see the factory shut down or move overseas. Instead of offering workers promised benefits, unions can be blamed for lost jobs and benefits.

This was the case with the Pillowtex textile mill in Kannapolis, N.C. In 1999 labor unions successfully organized the then-profitable mill, after a 25-year fight described as a “victory” for workers. But victory was bitter. In 2003 the plant closed, resulting in 4,800 layoffs, and Kannapolis has yet to fully recover.

While they claim to be “kicking ass for the working class,” some union bosses are, in fact, kicking union members by making false promises and spending dues money on their own high salaries and “official” getaways at fancy resorts. The steady decline in union membership over the past quarter-century, however, shows that the working class isn’t fooled.

Ms. Furchtgott-Roth, former chief economist of the U.S. Department of Labor, is a senior fellow at the Hudson Institute. Her paper, “Improving Union Financial Transparency,” was released by Hudson this week.