How to Keep Your Job When You're Over 50

The following commentary comes from an independent investor or market observer as part of TheStreet's guest contributor program, which is separate from the company's news coverage.

NEW YORK (TheStreet) -- Need to work longer before retiring? Older worker, beware! A bull's-eye is being stenciled on your back. This can put a crimp in the best-laid plans.

Fifteen percent of the unemployed are over 55. Of those out of work for more than a year, the over 55 represent 45%. This means only about 10% have found another job. These lucky workers though may not be dancing in the streets because most have taken wage cuts.

Is it discrimination? There is nothing illegal about hiring someone who isn't a good fit and there are plenty of reasons older workers may not be a good fit, such as being less productive, having dated skills and being averse to change.

Studies show mental abilities to reason peak in the late twenties and early thirties, reflexes and strength start to go around the same time. Verbal fluency is the last to go; it can last into the fifties. Generally productivity starts declining in the thirties.

Banking on experience being a productivity equalizer? A study in Finland found experience-related performance improvements peak at four years. Some speculate that the value of experience is on the decline; the culprit is the Internet. There are plenty of people sharing the tricks of the trade and all it takes is a clickety click.

Speaking of clickety click -- that's another reason productivity in older workers declines. They are less likely to leverage the many productive powers of technology because they don't need it. Who needs to bank online when you can hand write checks, retabulate balances, address envelopes, buy stamps and put them in the post?

A less productive, behind the times worker looking to maintain a salary twice a younger worker's rate are ample reasons for someone not to be a good fit.

So it's not really surprising that older job seekers are finding it tough going. For any midlifer that wants to keep their job, it's important to stay off a layoff short list and out of the boss' termination sights by staying productive and valuable -- earning your keep.