In Japan, "What's your type?" is much more than small talk; it can be a paramount¹ question in everything from matchmaking to getting a job.

By type, the Japanese mean blood type, and no amount of scientific debunking² can kill a widely held notion that blood tells all.

In the year just ended, four of Japan's top 10 best-sellers were about how blood type determines personality, according to Japan's largest book distributor, Tohan Co. The books' publisher, Bungeisha, says the series — one each for types B, O, A, and AB — has combined sales of well over 5 million copies.

Taku Kabeya, chief editor at Bungeisha, thinks the appeal comes from having one's self-image confirmed; readers discover the definition of their blood type and "It's like 'Yes, that's me!'"

As defined by the books, type As are sensitive perfectionists but overanxious; Type Bs are cheerful but eccentric and selfish; Os are curious, generous but stubborn; and ABs are arty but mysterious and unpredictable.

All that may sound like a horoscope, but the public doesn't seem to care.

Even Prime Minister Taro³ Aso seems to consider it important enough to reveal in his official profile on the Web. He's an A. His rival, opposition⁴ leader Ichiro Ozawa, is a B.

Nowadays blood type features in a Nintendo DS game and on "lucky bags" of women's accessories tailored to blood type and sold at Tokyo's Printemps department store. A TV network is set to broadcast a comedy about women seeking husbands according to blood type.

It doesn't stop there.

Matchmaking agencies provide blood-type compatibility tests, and some companies make decisions about assignments based on employees' blood types.

Children at some kindergartens are divided up by blood type, and the women's softball team that won gold at the Beijing Olympics used the theory to customize each player's training.

Not all see the craze as harmless fun, and the Japanese now have a term, "bura-hara," meaning blood-type harassment⁵.

And, despite repeated warnings, many employers continue to ask blood types at job interviews, said Junichi Wadayama, an official at the Health, Welfare and Labor⁶ Ministry⁷.

"It's so widespread that most people, even company officials, are not aware that asking blood types could lead to discrimination," Wadayama said.

Blood types, determined⁸ by the proteins in the blood, have nothing to do with personality, said Satoru Kikuchi, associate professor of psychology⁹ at Shinshu University.

"It's simply sham¹⁰ science," he said. "The idea encourages people to judge others by the blood types, without trying to understand them as human beings. It's like racism¹¹."

This use of blood-typing has unsavory roots.

The theory was imported from Nazi¹² race ideologues and adopted by Japan's militarist government in the 1930s to breed better soldiers. The idea was scrapped¹³ years later and the craze faded.

It resurfaced in the 1970s, however, as Masahiko Nomi, an advocate with no medical background, gave the theory mass appeal. His son, Toshitaka, now promotes it through a private group, the Human Science ABO Center, saying it's not intended to rank or judge people but to smooth relationships and help make the best of one's talents.

The books tend to stop short of blood-type determinism, suggesting instead that while blood type creates personality tendencies, it's hardly definitive¹⁴.

"Good job, you're done. So how do you feel about the results?" one blood type manual asks on its closing page. "Your type, after all, is what you decide you are."