Labor Day brings the end of summer, the beginning of school, and an annual reminder that "the folks who brought you the weekend" used to carry some serious clout. Unions' influence has since dwindled, and by last year only 12% of workers counted themselves card-carrying members.

However, if you're on a manufacturing line, or you're a teacher, police officer, firefighter, or librarian, the odds remain pretty good that a union representative will come knocking at your door. If you're thinking about signing up, you may be wondering what those union dues buy.

Let's set politics aside for a moment in favor of economics. After all, unions promise to make your standard of living better through increased wages and benefits. The first thing to know? It's no guarantee, especially when an entire industry faces challenges. Despite strong unions in the auto industry, thousands of jobs have been eliminated at GM (NYSE:GM), Ford (NYSE:F), and Chrysler. And unions haven't prevented slashed pensions at airlines like UAL's (NYSE:UAUA) United Airlines and Delta Airlines (NYSE:DAL).

To find out whether your union dues will be money well spent, ask some questions:

  • How much are the dues? Are they calculated as a percentage of your pay or as a flat fee? If they're a percentage of your pay, find out whether any future pay raises will be counted fully or partially toward that calculation. Don't assume that your union dues can be deducted from your taxes. They can, but they must (when combined with other professional expenses and other miscellaneous items) exceed 2% of your adjust gross income before you can start deducting them.
  • How will your dues be spent? If your local or national representatives can't answer that question, it may be a sign that the union isn't acting as a good steward of your money.
  • Find out whether the union stays active all the time, or whether it only gets organized when contract talks start. Ideally, you'd like your union to be paying attention to job matters even when they're not knee-deep in negotiations.
  • Talk to your shop steward to find out what kind of successes the union has had on behalf of workers, individually and as a group, in the past. What kind of resources does the union have to help you pursue a problem or a contract violation? If you can talk with an employee who has used the union grievance procedure to try to remedy a job wrong, that's even better.
  • Take a look at the contract, your salary, and your benefits and compare them to others in your industry. Are they better, or about the same? Even if they aren't ideal, has the union successfully staved off the erosion of benefits (like health and retirement perks) that has hit many workers?
  • Does the union actively defend the contract? If you work in a place where the culture means that employees don't claim the rights they have in the contract, you may find your dues don't come back to you in the form of the overtime pay or other apparent benefits.

If you ask all these questions and you aren't satisfied with the answers, you have one more reason to think about joining -- pay your dues and get to work changing the organization from the inside.

For some other ideas to help you get more from your job, take a look at these other Foolish articles:

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Fool contributor Mary Dalrymple used to be a card-carrying union member until she gave it up for more Foolish pursuits. She does not own stock in any company mentioned in this article and welcomes your feedback. The Motley Fool has an ironclad disclosure policy.