A trial has increased Americans interest in the problem of violence against women. O. J. Simpson has been accused of killing his former wife. Mrs. Simpson and a friend were stabbed to death outside her home in June, 1996. Reports say that Mrs. Simpson had called the police for help several times in the past few years. She reported that her husband had beaten her and she was afraid he would kill her. A jury was chosen, but it decided Mr. Simpson was not guilty. Domestic violence against women, especially wife beating, is a social problem in the U. S. Medical experts say wife beating is the most serious health threat to American women. The government says more young American women have been injured by men they know than by strangers, and more women are injured in this way than in accidents. Experts say violence against women takes place in almost every social, economic, racial and religious group. A federal crime study says that every year more than four million young American women are beaten severely. Most of the violence is done by their present or former husbands or by their boyfriends. In the past, many women were afraid to discuss the problem. They did not want anybody to know they were beaten by their husbands or boyfriends. Police usually refused to arrest a man who beat his wife, and the court did not take the issue seriously. Wife beaters were rarely sent to jail. Many women refused to take action against their husbands or boyfriends because they knew they would face even greater violence if they did. A serious movement against domestic violence began in the U. S. in the mid 1970s. Many activists were women who had been beaten. Since then great progress has been made. Activists have formed hundreds of local groups and set up many temporary homes for victims and their children. Progress has also been made in the justice system. Police and the courts now deal with the problem more seriously. In 26 states the police must now arrest wife beaters even if the victim does not cooperate. Questions: Whats the main topic of this passage?