Three Americans won the Nobel prize in economics for research into how information affects markets, while two U.S. chemists and a Japanese scientist won the chemistry award for discoveries used in producing medicines, including a now-standard treatment for Parkinson's disease.

The awards announced Wednesday by the Royal Swedish Academy of Sciences in Stockholm bring the number of American winners this year to eight, one more than last year.

George A. Akerlof, 61, of the University of California at Berkeley; A. Michael Spence, 58, of Stanford University; and Joseph E. Stiglitz, 58, of Columbia University will share the $943,000 economics award.

In the 1970s, they laid the groundwork for a general theory about how people with differing amounts of information affect markets. Their research has helped economists explain the boom in high-tech stocks during the 1990s — as well as its recent collapse.

"It first of all helps people understand better when markets perform poorly," Spence, 58, told the Associated Press by telephone. "All of us were given the award for trying to understand how markets perform when people have imperfect information."

In 1970, Akerlof began exploring the topic with a paper called "The Market for Lemons" that used car sales as an example.

"Markets such as for used cars tend to be rather screwed up," Akerlof told The Associated Press on Wednesday.

"When you buy a used car you're always careful because you're wondering why that person is selling the car. When you're selling, you're worried you're not going to get a good price," he said. "People are suspicious."

The winners' works "form the core of modern information economics," the academy said.

Earlier Wednesday, the prize for chemistry went to Ryoji Noyori of Nagoya University in Japan and Americans William S. Knowles of St. Louis and K. Barry Sharpless of the Scripps Research Institute in La Jolla, Calif.

Their research deals with the fact that many molecules appear in two forms that are mirror images of each other. When used in medicines, some forms can aid the body while their opposites can be harmful.

One example of this dual nature is the drug thalidomide, which was used by pregnant women in the 1960s. One form of the drug helped control nausea, while its opposite form caused birth defects.

The Nobel winners' research, some of which dates back three decades, has produced ways of making only right form of molecules. These methods have been used to manufacture antibiotics, heart medications, anti-inflammatory drugs and ulcer treatments.

While working for the Monsanto Co. in 1968, Knowles found a way to make L-dopa, which is used to treat Parkinson's disease, without producing its mirror image.

"This was the first time this kind of a thing had been done," Knowles, 84, told The Associated Press on Wednesday. "The field has since burgeoned and the other people who were with me in this thing have enlarged the field enormously."

Noyori, 63, developed substances that encourage particular chemical reactions, making it easier for companies to produce large amounts of antibiotics and other drugs.

Sharpless, 60, in 1980 did experiments that led to a method for manufacturing beta-blockers, a widely used class of heart drugs.

His research has been described by many scientists as "the most important discovery in the field of synthesis during the past few decades," the academy said.