AS concerns about the economy have faded in 1996, crime has emerged as one of the dominant political issues. To some, this may seem puzzling. After years of partisan wrangling, a significant crime bill was enacted in 1994, and more police are now appearing on our streets. Sentences have been lengthened, and the number of incarcerated Americans has more than doubled. Violent crime has actually declined through much of the 1990s, especially in large cities.