College students, and parents concerned about their kids’ careers, often try to divine which jobs or skills will be in demand when it’s time to enter the workforce. With today’s quickly shifting economies and technologies, it can be tough to hit that moving target.

Some resort to choosing broad categories. In the U.S., for instance, there has been a steady media drumbeat about the deficit in science education. For those who are science oriented, that might seem to make planning research careers in, say, chemistry, genetics or neuroscience a safe bet. But it’s not. Despite today’s high-tech, health care-oriented world, many PhDs in these areas are unemployed or floundering in lower level jobs, according to this article in the Washington Post. The jobs just are not there.

Here’s another straw in the wind: Only 38% of those with a new PhD in chemistry had jobs last year, according to a survey by the American Chemical Society, the Post notes.

This is unsettling, not only for well-educated scientists who can’t find appropriate positions – or are being laid off – but also for those trying to plan for future jobs requiring a long lead time to accumulate skills that are not easily transferrable. As the article notes, we all tend to think that more education is always a good thing, especially in a growing, technical field like health care. Yet it’s not true, given the quickly changing supply/demand curve for positions requiring such technical expertise. For example, while the number of PhDs churned out between 2003 and 2007 in the medical and life sciences nearly doubled, the job pool did not keep up and lately has shrunk in the U.S., the Post notes.

One woman, who studied to be a brain scientist, gave up looking for a permanent job in her field and accepted a lessor position three years after receiving a doctorate in neuroscience, the Post reports. “I’ve listened to this stuff on the news about how we need more scientists and engineers,” she said. “I’m thinking, ‘What are you talking about?’ We’re here.”

So, how can you know these things in advance? You can’t.

“The jobs haven’t been there for quite some time,” says Peter Cappelli, head of Wharton’s Center for Human Resources. “Despite the rhetoric about the need for more scientists, the reports that look carefully into the labor market for scientists have found that supply has long outstripped demand. That is why there are so many post-doc programs for PhD scientists, because there aren’t enough good real and permanent jobs for those who graduate.”

What’s more, “the other problem with most technical careers now is that they don’t last long,” Cappelli adds. “There isn’t much retraining available, and skills become obsolete quickly. When they do, the old workers are pushed out.”

In the Post article, another woman in her early 50s who had spent 20 years designing new drugs for large pharmaceutical companies and who was laid off not long ago, said she was planning to “get out of science.” But she also had advice for her daughter, who “loves chemistry and math. I tell her, ‘Don’t go into science.’ I’ve made that very clear to her.” In her industry, “it’s been a bloodbath…. Very good chemists with PhDs from Stanford can’t find jobs.”

So, is there any advice Cappelli can offer students, especially those in science, on how they can plan a career path? “Frankly, no,” he says. “It’s better to be adaptable than to try to plan your way to success.”