Worried that your personal information is being collected and manipulated? Wonder why your favorite websites know your taste in books and movies better than your own mother does? 

, Ian Ayres answers these questions and more as he tells a numerical tale both exciting and ­cautionary.

In the past several years, advances in computer storage capacity have made possible massive databases that are changing the ways government agencies, market research firms, and universities run their ­operations—­and our lives. Ayres, an economist and law professor at Yale, sets out to explain how these databases, some of which contain thousands of times the information stored in the Library of Congress, can be quickly analyzed to shape ­real-world decisions.

Super Crunchers is not the dry econometrics textbook you couldn’t get through in college. Ayres relies on baseball scouts, wine critics, entrepreneurs, and doctors to illustrate his argument, and goes into the gory mathematical details only in the last chapter. He illustrates ­regression—­a statistical procedure that exploits databases to estimate how var­ious factors influence a single outcome—­by describing how electronic matchmaking sites such as eHarmony and True.com put people together. These companies propose matches by collecting clues to personality traits and social skills with detailed questionnaires. The clues become data, which are then crunched to calculate how compatible one person might be with others who have also submitted information. Sometimes, opposites do attract.

The basic idea underlying super crunching is that using regression techniques produces far more accurate results than the intuition and experience of the traditional expert. The debate over how decisions should be made is nowhere clearer than in Ayres’s chapter on ­“evidence-­based medicine.” No human brain, even that of a good doctor, can actively recall all 11,000 human diseases and their symptoms. Enter the Isabel database, which serves as the “Google of medical diagnosis.” The doctor logs a patient’s symptoms, and Isabel generates a list of possible diagnoses. In about 10 percent of cases, Isabel points doctors toward a diagnosis they didn’t consider but should ­have.

, he does leave a role for the gut. People are bad at weighing the relative importance of factors that affect a given outcome, but they have good hunches about which variables should be considered in the first place. Databases alone do not always yield definitive results; some have been so manipulated that they resemble “prisoners who will tell you anything you want to know.” Ayres advises all crunchers to check their assumptions carefully and, if possible, to allow results to be independently verified.

He offers the cautionary tale of John Lott, a scholar who, in 2000, created and analyzed a crime database and found that when citizens are allowed to carry concealed weapons, ­would-­be attackers are discouraged and crime decreases. Lott’s conclusions were instrumental in the passage of at least nine state laws permitting concealed weapons. When he shared his database with Ayres and others, however, they discovered that slight changes to the regression equations negated the more guns/less crime relationship, and that after coding errors were corrected, the data set suggested that con­cealed weapons laws are, if anything, likely to increase crime ­rates.

A couple of years ago, Malcolm Gladwell made the case for intuition. In 

, he argued that instantaneous, subconscious decisions based on accumulated knowledge and experience are often superior to those derived from “more deliberate and exhaustive ways of thinking.”

What Ayres and Gladwell do agree on is that the brain does not make good decisions when flooded with information. We are biased by preconceived ideas, prone to rationalization, and easily influenced. We think we are right far more often than we are. After reading Ayres’s book, some may be ready to throw intuition to the wind. The more cautious among us will take comfort in Gladwell’s conviction that the human mind may still yield insights not readily supplanted by those of a computer.

Super Crunchers: Why ­Thinking-­by-­Numbers Is the New Way to Be ­Smart

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Trying to come to grips with the myriad ways that numbers rule our lives, and to understand that some thinking is better done by human than computer.

How numbers rule our lives

 is the story of the resolute and plucky lawyers (many female, some male) who tackled one obstacle after another to reverse ­gender-­based discrimination in the United States. Fred Strebeigh, a writer who teaches nonfiction at Yale, draws us into his tale by tracing the careers and accomplishments of U.S. Supreme Court justices Ruth Bader Ginsburg and Sandra Day O’Connor, feminist legal scholar Catharine MacKinnon, and many ­lesser-­known but no ­less-determined women. All the action takes place in the few short decades since American law schools began admitting women in more than token ­numbers.

Strebeigh begins with the fight against rules that arbitrarily preferred men over women in the allocation of government rights and benefits. As a law professor at Rutgers and then Columbia, Ginsburg worked with a few close allies to advance cases that strategically undermined the Supreme Court’s interpretation of the Fourteenth Amendment’s equal protection clause. Since the amendment’s enactment in 1868, the Court had not subjected the charge of discrimination against women to the same scrutiny as a charge of racial discrimination. Only as a Supreme Court justice herself did Ginsburg finally succeed in nudging the Court to apply “skeptical scrutiny”—though still not the highest standard of “strict scrutiny”—to laws that may violate the U.S. Constitution’s promise of “equal protection of the laws” for women. In 1996, in 

, she wrote the majority opinion finding that the Fourteenth Amendment required the exclusive Virginia Military Institute to admit ­women.

Elsewhere, Strebeigh examines the struggles to open law schools and the legal profession to women, to ensure that pregnant women were not discriminated against, and to codify sexual harassment and domestic violence as crimes. The narrative of incremental legal change is enlivened by Strebeigh’s gift for fleshing out the human drama underlying key cases. His extensive interviews with those who prepared and argued those cases, as well as the use of Court and personal archives, allow him to piece together some of the personal dynamics on the Supreme ­Court.

Strebeigh is particularly good at dramatizing how the Supreme Court works, and how it vies with Congress to shape the law. For example, he devotes a chapter to the 1976 case 

, which arose because GE (which employed 100,000 women) excluded conditions relating to pregnancy from its disability plan, in part because of the cost. In the words of GE president Gerard Swope, “Women did not recognize the responsibilities of life, for they probably were hoping to get married soon and leave the com­pany.” In the Court’s majority opinion, William Rehnquist wrote that the 1964 Civil Rights Act did not define the word “discrim­ination” in a way that made it clearly illegal to discriminate against pregnant women. An outraged Congress quickly passed what became the Preg­nancy Discrimination Act, which President Jimmy Carter signed in ­1978.

The parallel between the struggle for equality for people of color and efforts to apply civil rights protections to ­women—­which came ­later—­runs through Strebeigh’s account. President John F. Kennedy signed the Equal Pay Act of 1963 just before introducing a draft of the legislation that would become the 1964 Civil Rights Act. The draft only prohibited discrimination on the basis of race, color, religion, or national origin. A Virginia congressman proposed adding “sex”—he said later, “as a joke”—as an additional category in Title VII, the section that concerned employment, hoping this would kill the bill. It didn’t. But enforcement was another matter: For years, the newly created Equal Employment Opportunity Commis­sion dealt grudgingly with cases of gender discrimination. Susan Deller Ross, a lawyer who joined the EEOC in 1970 to work on women’s rights, recalls being greeted by a female colleague who grumbled bitterly, “I hear you’re one of those feminists.”

 is a sobering reminder that these battles were fought within the lifetime of any woman older than 30. In the absence of a ratified constitutional amendment guaranteeing women equal rights, recognition that women are entitled to the same legal protections as men has emerged gradually. This book generates a genuine appreciation for the legal entrepreneurs who fought long and hard to make possible the careers of many a professional woman, including this ­one.

 is a senior scholar at the Woodrow Wilson Center.

 by Fred Strebeigh, Norton, 582 pp, 2009.

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Alexandra Vacroux on women's legal rights.