With black unemployment reaching historic levels, banks laying off tens of thousands and law school graduates waiting tables, why aren’t more African-Americans looking toward science, technology, engineering and math — the still-hiring careers known as STEM?

The answer turns out to be a complex equation of self-doubt, stereotypes, discouragement and economics — and sometimes just wrong perceptions of what math and science are all about.

The percentage of African-Americans earning STEM degrees has fallen during the last decade. It may seem far-fetched for an undereducated black population to aspire to become chemists or computer scientists, but the door is wide open, colleges say, and the shortfall has created opportunities for those who choose this path.

STEM barriers are not unique to black people. The United States does not produce as high a proportion of white engineers, scientists and mathematicians as it used to. Women and Latinos also lag behind white men.

Yet the situation is most acute for African-Americans.

Black people are 12 percent of the U.S. population and 11 percent of all students beyond high school. In 2009, they received just 7 percent of all STEM bachelor’s degrees, 4 percent of master’s degrees, and 2 percent of PhDs, according to the National Center for Education Statistics.

From community college through PhD level, the percentage of STEM degrees received by blacks in 2009 was 7.5 percent, down from 8.1 percent in 2001.

The numbers are striking in certain fields. In 2009, African-Americans received 1 percent of degrees in science technologies, and 4 percent of degrees in math and statistics. Out of 5,048 PhDs awarded in the physical sciences, such as chemistry and physics, 89 went to African-Americans — less than 2 percent.

Several factors are cited by scientists, educators and students. One is a self-defeating perception that STEM is too hard. Also mentioned are a lack of role models and mentors, pressure to earn money quickly, and discouraging academic environments.

The impact reaches beyond the black community as America struggles to produce enough scientists to prosper in a world ruled by technology.

“White men make up less than 50 percent of the U.S. population. We’re drawing (future scientists) from less than 50 percent of the talent we have available,” says Mae Jemison, the first black woman astronaut, who has a medical degree and a bachelor’s in chemical engineering.

“The more people you have in STEM,” she says, “the more innovations you’ll get.”

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Jemison says the problem begins for children of all backgrounds in grade school, where they are usually asked to memorize facts out of a book instead of satisfying their natural curiosity through experiments and exploring. She also says many primary school science teachers took little science in college.

Allen Gordon has been teaching math in Oakland, Calif., for seven years. He always tries to apply real-word situations to his lessons — coupons, compound interest on bank accounts, album sales.

“If math and science seem boring and of no use on a primary education level, who would want to pursue it while in college?” he says. “Especially when you don’t see many, if any, black men or women teaching.”

“Math and science are not something that black men and women sit around and pontificate about at home, dinner parties, the sports bar, hair salon, et cetera,” he says. “It doesn’t fit into their social idea of status.

“Let’s face it, there is no glory in saying, ‘I teach math or science.’ Career school teachers still seem to be very proletarian.”

Even some of Gordon’s fellow teachers ask how he can teach math, saying, “Funny, you don’t look like the nerd type.”

That’s a stereotype Jemison knows well.

“The media images you see of scientists are older white males who are goofy or socially inept in some way,” she says. “That’s the mad scientist, the geek” — and it doesn’t include role models for young black and Hispanic students.

Jemison, who watched “Star Trek” growing up, declines to call the black female character Lieutenant Uhura an inspiration, but the fictional space traveler did affect her.

“Her character was really an affirmation that my assumptions about going into space were shared by others, and that everyone had a right and a role to play. So that affirmation, for a little kid growing up, it’s an image of possibilities.”

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Growing up in Murfreesboro, Tenn., Christopher Smith used to tutor fellow black students at his high school.

The students would often start solving a complicated math problem by doing everything right. “Then they would say, ‘I don’t know what I’m doing!’” recalls Smith, now pursuing a PhD in biomedical engineering at Johns Hopkins University.

He thinks some African-Americans psych themselves out of STEM.

“Today I talk to friends back home, and they say, ‘I wouldn’t be able to do good in college anyway.’ A lot of it is just confidence,” Smith says. “If people convince you that science and math is harder than everything else, and you already have low self-esteem, maybe that’s one reason there are so few black scientists.”

“Few” is a generous term in Smith’s field of biological and biomedical sciences, where 6,957 PhDs were awarded in 2009. Only 88 went to black men — that’s 1 percent. (176 went to black women.)

LaMont Toliver also sees a problem with what he calls “self-doubt.” He is director of the University of Maryland Baltimore County’s Meyerhoff Scholars Program, a national leader in increasing STEM diversity.

“Advanced placement courses, calculus, chemistry, these are hard courses,” Toliver says. “Some of them believe that they just can’t do it. . Then you couple that with a lack of encouragement.”

“If we were more supportive as a community, as parents and providing guidance and mentoring at an early age, then more African-American students would do it.”

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Money is another factor in the STEM disparity. It takes many years after college to get the advanced degrees needed to become leaders in math and science fields — university professors, directors of research labs, heads of engineering departments — and some black students can’t afford to wait that long.

Before one recent New Year’s Eve, Smith, the Johns Hopkins student, was debating whether to purchase a bus ticket from Baltimore to New York City to hang out with friends. It was a tough decision — the ticket cost $37.

Smith, 27, received a fellowship for black scientists this year from Merck and the United Negro College Fund. As he works toward his PhD, Smith lives on a salary and stipend of about $25,000 per year.

Like many black students, Smith comes from modest means. His mother was a homemaker with a high school diploma; his father earned a GED, became an electrician and eventually owned a business.

“I get paid to go to school, so I don’t want to complain,” Smith says.

But he’s still several years away from completing his PhD, and he’s tired of agonizing over a $37 bus ticket. Even after he gets that degree, he’ll need to do a year of post-doctoral study. “If I stay here at Hopkins” for post-doc work, he says, “I’ll make the same or less than a city sanitation worker.”

At each stage of science education, many black students feel pressure to stop studying and start earning real money. Smith, who has an undergraduate degree from MIT, says he could be making as much as $115,000 per year in a corporate job.

Yet it’s hard to advance far in science without at least a master’s, if not a doctorate.

Joseph Francisco, a black chemistry professor at Purdue and past president of the American Chemical Society, has a PhD from MIT. He says his undergrad students are always telling him, “I got to think about a job.”

“With first-generation college students, there is enormous pressure,” Francisco says. “Without a mentor who can tell you about what to expect beyond undergrad, who can explain what are the opportunities after a postgraduate degree, they just stop at a bachelor’s degree.”

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Francisco mentions another source of pressure affecting black STEM students: isolation.

In 1981, Francisco was studying at MIT when he heard about a national organization for black chemists. He went to its convention, in Chicago.

“It was incredible,” Francisco remembers. “I remember having the feeling, ‘you are not alone.’ That sense of isolation can be powerful.”

It was different when he was growing up on the black side of segregated Beaumont, Texas. He was raised by his grandmother, who had a third-grade education, and his grandfather, who laid concrete pipes. There was a black pharmacist in his neighborhood, and Francisco worked part-time in the shop. There was a black doctor, teachers, a college professor.

That changed when he went to the University of Texas and then MIT, where there were few black faces.

In a 2010 Bayer Corp. survey of 1,226 women and underrepresented minority chemists and chemical engineers, 40 percent said they were discouraged from pursuing a STEM career. Sixty percent said college was where most of the discouragement happened.

Jemison, the astronaut, says that while at Stanford, “some professors were not that thrilled to see me in their classrooms.”

“Stereotypes impact the people who have an opportunity to influence your career,” she says. “They don’t see you as a peer.”

After receiving his PhD, Francisco had several job offers. He chose Wayne State University in Detroit, and would later become president of the National Organization for the Professional Advancement of Black Chemists and Chemical Engineers.

“I saw an opportunity at Wayne State to do good science in a supportive place that gave me the flexibility to make a contribution to the community,” he says. “To give something back, to a black community.”

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In the world of atoms and numbers, does the color of the person who studies them really matter?

Many of America’s technology giants say, yes. Merck has funded tens of millions of dollars in United Negro College Fund scholarships. Bayer has a special focus on recruiting and promoting minorities. Technology giants such as Boeing, General Electric and Xerox support organizations dedicated to raising black STEM participation.

Their motivation is simple math. If bright and capable students’ talents go undeveloped, “this represents a loss for both the individual and society,” the National Science Board said in a 2010 report.

The report said that after the Soviet Union beat America into space with Sputnik, the U.S. was inspired to educate a new generation of innovators. This national urgency faded by the 1970s, the report said, and was replaced by complacency.

Some 16 percent of all U.S. undergraduates major in natural science or engineering, compared with 25 percent in Europe, 38 percent in South Korea and 47 percent in China, the report said.

To reverse this decline, the report said America must “cast a wide net to identify all types of talents and to nurture potential in all demographics of students.”

Jemison identifies another incentive. Even though scientists may use the same methodology, “what topics they choose to research, even the interpretation of facts or what they choose to look at is influenced by experience.”

“So many times it’s the diversity of thought and perception and experience base that starts to make the difference in the problems you research and the solutions you consider,” she says.

“It’s a much more robust reason for diversity that just the head count.”

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Copyright 2011 The Associated Press.