Pros and cons to each demographic

Younger workers, for instance, typically need mentoring and guidance, while older workers—with more experience and knowledge—likely will be looking for jobs that offer them a better chance to prepare for a delayed retirement or to keep ahead of expenses in the wake of the Great Recession's effects on their retirement savings, but also to take on new challenges to use their skills.

Employers tend to have a negative view of older workers that is often misplaced and mistaken. They categorize them as slower, less able to perform complex tasks and, for women in particular, worthy only of lesser, lower-paying jobs. Some of this is the fault of Hollywood, which often characterizes older people in demeaning ways.

But whether influenced by movies or not, the facts are that older people are increasingly being shut out of higher-paying jobs—for that matter, any jobs—as they age. And that's to the detriment not only of themselves and their eventual retirement, but to their employers and even the economy, which depends to a large extent upon the 50+ crowd to keep the financial wheels turning.

Crystallized intelligence vs. fluid intelligence, experience vs. speed

In fact, even the Bureau of Labor Statistics fails to take into account the extent to which older people are being relegated to lower-wage service jobs. A November 2016 blog post from the Schwartz Center for Economic Policy Analysis at the New School reported that "In September, 27.1 percent of full-time workers aged 55 and older were in low-wage jobs compared to 19.0 percent of younger workers." And if there's one thing a low-wage job won't (and can't) do, it's allow the worker adequately to prepare for retirement.

While it's true that there can be some decline in cognitive aging that could affect some older workers in some fields, according to a study from the Center for Retirement Research at Boston College, it truly depends on the individual worker and the type of job.

In many cases, experience (termed in the paper "crystallized intelligence" and defined as accumulated knowledge) can be more important than the speed at which a person works (termed "fluid intelligence" and defined as "the capacity to process new information").

So even if an older worker's fluid intelligence might not be what it once was, it may not matter, since crystallized intelligence may be more important—particularly toward the end of a long career, when depth of knowledge and background can play a vital role in a job well done.

Conquering ageism as well as finding a good job

When a senior is determined to stay in the job market, whether out of financial necessity or out of a love for the mental challenges and stimulus, having to conquer such mistaken beliefs can add to the challenge of finding a job that will pay a decent salary and allow them to set aside money for retirement.

Those fortunate enough to capture a consultant gig that pays well have the advantage of being able to use their talents to capacity, but others aren't so fortunate—and that can hurt in more ways than lost pay, weighing on their sense of self-worth and even damaging their health.

Mix of older and younger workers benefits companies

But employers can avoid that by being more creative about their hiring practices.

They can make sure their workforce contains both older and younger workers, so their companies will benefit from the experience of the former and the skills and energy of the latter.

One strategy is to provide part-time jobs, at decent pay, that can ease older workers into retirement while at the same time allowing them to train successors and mentor younger employees lacking knowledge and experience.

Not only does this benefit both sets of workers and the employer by retaining knowledge that could otherwise be lost, but it also creates a more stable work environment less subject to disruption by the brain drain of older workers leaving.

Whether your company is filled with young workers, older ones or a blend of the two, here's a look at CareerBuilder's list of which cities have the highest increases in an aging workforce.

10. Springfield, Massachusetts

Total Population in 2016: 633,755

Share of Workers Ages 55+ in 2016: 24.1 percent

Change in Share of 55+ Workers, 2001–2016: 0.9 percent

9. Tucson, Arizona

Total Population in 2016: 1,016,717

Share of Workers Ages 55+ in 2016: 21.9 percent

Change in Share of 55+ Workers, 2001–2016: 1.0 percent

8. Portland-Vancouver-Hillsboro, Oregon/Washington

Total Population in 2016: 2,416,242

Share of Workers Ages 55+ in 2016: 21.7 percent

Change in Share of 55+ Workers, 2001–2016: 1.1 percent

7. Boise City, Idaho

Total Population in 2016: 688,355

Share of Workers Ages 55+ in 2016: 19.7 percent

Change in Share of 55+ Workers, 2001–2016: 1.1 percent

6. Albany-Schenectady-Troy, New York

Total Population in 2016: 884,310

Share of Workers Ages 55+ in 2016: 22.2 percent

Change in Share of 55+ Workers, 2001–2016: 1.2 percent

5. Spokane-Spokane Valley, Washington

Total Population in 2016: 551,091

Share of Workers Ages 55+ in 2016: 21.7 percent

Change in Share of 55+ Workers, 2001–2016: 1.3 percent

4. Sacramento–Roseville–Arden-Arcade, California

Total Population in 2016: 2,296,511

Share of Workers Ages 55+ in 2016: 21.2 percent

Change in Share of 55+ Workers, 2001–2016: 1.3 percent

3. Virginia Beach-Norfolk-Newport News, Virginia/North Carolina

Total Population in 2016: 1,734,618

Share of Workers Ages 55+ in 2016: 19.5 percent

Change in Share of 55+ Workers, 2001–2016: 1.3 percent

2. Oklahoma City, Oklahoma

Total Population in 2016: 1,376,790

Share of Workers Ages 55+ in 2016: 21.0 percent

Change in Share of 55+ Workers, 2001–2016: 1.5 percent

1. North Port-Sarasota-Bradenton, Florida

Total Population in 2016: 779,799

Share of Workers Ages 55+ in 2016: 25.8 percent

Change in Share of 55+ Workers, 2001–2016: 1.5 percent

North Port has experienced the greatest increase in the share of workers ages 55+ from 2001 to 2016, giving it the largest overall share of workers ages 55+—but it's also seen the greatest decrease in millennials over the same period.

North Port also has the largest overall share of 55+ workers; the next highest concentrations of 55+ workers are in New Haven, Connecticut, with 24.9 percent; Pittsburgh, Pennsylvania, with 24.7 percent; Hartford, California, with 24.4 percent; and Deltona, Florida, with 24.4 percent.

Meanwhile, among the 10 most populous cities in the country, Philadelphia, Pennsylvania (23.1 percent), Miami, Florida (23.0 percent) and New York, New York (22.8 percent) have the largest share of workers ages 55+.