Even in a tough economy, older workers are valued in some industries. Technology-oriented companies that depend on experienced scientists and engineers are very worried about brain drain as the huge baby boomer generation retires. Many are scrambling to implement retention programs aimed at keeping these high-value knowledge workers on the job as long as possible. Some offer flexible work arrangements to accommodate the changing lifestyle needs of older employees.

What if you’re not a rocket scientist? Surveys suggest that many employers do value the loyalty, experience and reliability of older workers. Some also say older workers are more productive-and that their higher productivity offsets their higher compensation and benefit expenses. One study, for example, attempted to quantify productivity and cost advantages of retaining and hiring older workers by showing that turnover and training costs can exceed 50 percent of a worker’s annual salary, while higher compensation and benefit costs for older workers was only marginally higher than for younger people.

The jobless rate for older workers has been lower than average even as the recession accelerated; in April 2009, for example, the jobless rate for workers over 55 was 6.4 percent-much lower than the 8.9 percent unemployment rate for the nation as a whole.

Another bit of good news is the ongoing shift away from physical work in the U.S. labor market-a trend that benefits white-collar older workers who want to stay on the job. The percentage of workers in blue-collar occupations fell from about 3 percent in 1971 to 24 percent in 2007, while the percentage of people in management, professional and service occupations increased greatly (from 63 percent to 76  percent).

Where are the most hospitable employers for 50+ workers? One hint can be found in AARP’s annual award for the “Best Employers for Workers over 50.” The award offers a snapshot of the most age-friendly large employers in the country, and points toward age-friendly industry groups.

The selection criteria include recruiting practices; opportunities for on-the-job training; education and career development; flexible work arrangements; and employee and retiree benefits, such as pensions. AARP has been bestowing the awards since 2001, and the winner’s circle usually is crowded with health care companies, higher educational institutions, and corporations with progressive reputations. A smattering of financial services companies has made the list, too.

One group of researchers at The Urban Institute-a Washington, D.C. think tank that studies issues related to aging-tried a different tack. They decided to identify the most promising areas of opportunity for older workers by analyzing industries expected to experience rapid growth in the coming years and then cross-matching them with fields that will experience high turnover due to retirement.

Underneath some of the more optimistic numbers are a number of hard truths about the job market for older workers:

Unemployment lasts longer. While the jobless rate among older workers is lower than the general population, the length of joblessness is much higher for older workers. Unemployed workers over age 45 required an average of 22.2 weeks to find new work in 2008, compared with 16.2 weeks for younger workers.

The impact of a layoff is bigger. When older workers lose their jobs, they face the reality that they may not work again fulltime-a blow that can wreck even carefully laid retirement plans. Household wealth typically takes a hit as high as 23 percent for single people and 19 percent for married couples.

Earnings shrink. Even when older workers do land new jobs, they typically experience a steep drop in income and benefits. Median wages for people who take new jobs in their fifties fall by a median of 57 percent, and 25 percent lose their health insurance.

Age discrimination is routine. It’s illegal for employers to discriminate based on age in hiring and firing practices under the Age Discrimination in Employment Act of 1967. But it’s widely acknowledged to be a factor in job loss and hiring practices-something that should be obvious to even a casual reader of newspapers, which routinely run articles about laid-off midlife workers.

In 2005, a researcher from the National Bureau of Economic Research wanted to measure the response of employers to applicants of varying age who responded to job postings. Joanna Lahey sent out 4,000 resumes for fictitious female applicants to companies that had run newspaper ads for open jobs in Boston, Mass. and St. Petersburg, Florida, with ages ranging from 35 to 62. She indicated the fictitious applicants’ ages by listing the date of high school graduation.

Lahey found that a younger worker was more than 40 percent more likely to be called back for an interview than an older worker, when “older” was defined as age 50 or higher. In 2008, age discrimination claims related to layoffs filed with the Equal Employment Opportunity Commission were at a record high, and they were up 29 percent compared with 2007.

Working past page 50 isn’t a hopeless cause-far from it. But it’s important to approach the employment market with a sense of realism.