We like to tell ourselves that age is simply a number, especially those of us showing a few gray hairs and moving a little slower. However, if you've been looking for a job or trying to move up the corporate ladder, your age could be an obstacle.

Think about the last time you lost a workplace opportunity. Did the hiring manager think you were too old? Were you passed over for a promotion in favor of someone clearly less grizzled? If your age was used against you, you might have an age discrimination claim.

The U.S. Equal Employment Opportunity Commission (EEOC) defines age discrimination as "treating an applicant or employee less favorably because of his or her age." The federal Age Discrimination in Employment Act protects individuals over the age of 40 in a range of employment actions including hiring, firing, pay, promotions, job assignments, layoffs, trainings and benefits.

The law may be crystal clear about the protections older workers have, but actually proving ageism can be tricky. Let's say you weren't offered a job for which you applied. How will you be able to prove that the decision was based on your age, rather than your ability, experience, or other legitimate job qualifications? If a younger co-worker got the promotion you were angling for, can you honestly make a case that the company's decision was driven by age considerations, as opposed to something else?

Sadly, age discrimination in the workplace is all too real and much too common. A recent study by insurer Hiscox found that one in five workers age 40 and older reported experiencing discrimination in the workplace because of their age. Of those workers, less than half filed a charge or made a complaint, either because they didn't know how to do it or because they were worried about negative repercussions in the workplace.

To make matters worse, workers who saw another worker being subjected to age discrimination tended to keep their mouths shut. More than half didn't say anything because they were afraid of retaliation from their employer.

This isn't an insignificant issue. More than two-thirds of study respondents 65 or younger said they plan to continue working after they turn 66, but almost half of them said they had left a company due to experiencing or witnessing age discrimination.

Educate yourself. Most respondents to the Hiscox study said that ageism wasn't even included in bias training they got from their employers. If you don't know your rights, how can you be expected to assert them? Here's what you need to know.

The Age Discrimination in Employment Act of 1967 (ADEA) makes it unlawful for employers "to fail or refuse to hire or to discharge any individual or otherwise discriminate against any individual with respect to his compensation, terms, conditions, or privileges of employment, because of such individual's age." Employers can't "limit, segregate, or classify... employees in any way which would deprive or tend to deprive any individual of employment opportunities or otherwise adversely affect his status as an employee, because of such individual's age." Finally, it's against the law for employers to discriminate against employees or applicants because they have "opposed any practice made unlawful by this section, or .... made a charge, testified, assisted, or participated in any manner in an investigation, proceeding, or litigation under this chapter."

Bottom line: Your age can't be the reason you didn't get a job offer or a promotion, nor can it be used to reduce your pay or benefits, and any employer who retaliates against you for standing up for yourself is breaking the law.

Take action. If you suspect that you've been subject to age-based discrimination, take action. If you feel comfortable doing so, start with your HR department and give them a chance to investigate. You can also file a claim with the EEOC or an appropriate state agency.

An investigation might turn up facts that support your claim, in which case you might have another chance at that job or promotion, or you may be entitled to monetary compensation. At a minimum, you should have answers to your questions - even if the answer is that someone else was a better-qualified candidate.

Be proactive. Even when companies don't intend to discriminate, we know that recruiters subconsciously know who they're looking for. If a resume shouts, "I've been around a long time," they may be disinclined to move it forward. I advise my clients to provide information that conveys skills and experience without focusing on dates. Discretion is not dishonesty.

For older workers with significant educational or professional backgrounds, employers might assume that there are high salary expectations. If this isn't the case, be direct. In your cover letter, make it clear that you're happy to be paid whatever they've budgeted for the position. You can even point out the bargain they'll be getting, given your insights and years of experience.

Stay positive. A recent study in found many older patients seeking anti-aging procedures because of their concerns about age discrimination. The study found a negative relationship between perceived age discrimination and self-rated health, including lower self-esteem. It concluded that psychological counseling might be more helpful than dermatological intervention.

The more you understand your own goals and aspirations, the better prepared you will be to weather the verities of the job market. Stay positive and take good care of yourself as you apply for jobs or seek advancement in your career. Being educated about your legal rights will provide additional tools and support on your journey.

Gerald Sauer, founding partner at Sauer & Wagner LLP , is a veteran civil trial attorney who specializes in business, employment and intellectual property law.

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