(ISNS) -- In the last 15 years, something dramatic has happened in New York City: the crime rate has dropped precipitously, making the city -- where crime once was of epic proportions -- the safest major city in America.
How that happened is a matter of considerable controversy, with popular theories ranging from fiercer policing, to abortion, lead paint, and computer-assisted crime prevention programs.
David Greenberg, a sociologist at New York University, believes none of the theories stand up on their own. It could be all or none of the above, he said.
It could also be that Western civilization is just becoming more civilized and less violent, and it is finally showing up in the statistics, even with recent mass shootings in the United States.
Crime rates have fallen in most of the Western world as well as most American cities, but what has happened in New York City, with a population of 8 million, is extraordinary. The rate of violent crime began to decrease in the 1980s, before jumping in the 1990s when crack cocaine made it to the streets in many cities. Then it sank and has continued to do so.
In 1990, there were 2,245 murders in the city. Last year the number was 414, the lowest since police began keeping reliable records.
In one remarkable day, Nov. 26, 2012, there was not a single murder, stabbing or shooting reported in the nation's largest city, possibly the only time that happened since New York was a small Dutch colony.
"The analysis for homicide showed that rates dropped in every precinct although more in some than in others," Greenberg wrote in an article published in Justice Quarterly about the current trend. The same is true for other violent crimes, including robberies and assaults.
Greenberg said experts typically offer two common explanations. One is that in 1994 the New York Police Department installed CompStat, a computer program that tracks crime and allows police departments to manage personnel better. Another is the "broken windows" theory: police rigidly enforce misdemeanor crimes in an attempt to change the culture. Essentially, the police department believed that cracking down on offenses from prostitution to begging and excessive noise could help suppress felony crime. Either way, the NYPD takes credit.
For CompStat, the crime rate had already begun dropping when the software was installed. Greenberg also failed to find a causal relationship between an increase in misdemeanor charges and the overall crime rate.
Other theories also have been proposed. Steven Levitt and Steven Dubner, in the book "Freakonomics," proposed the increase in legal abortions was a factor. There were fewer young males, the demographic sector most responsible for crime. Malcolm Gladwell, in the book "The Tipping Point," said the increased police activity was just the last factor that ended an epidemic already ebbing. Both theories are highly controversial.
Another theory credits removal of lead from gasoline and paint. Lead causes brain damage and could account for some criminal activity so when lead was removed from gasoline and paint, fewer children were affected.
Greenberg said the evidence to support all those theories is weak.
So what is the answer?
Surprisingly, some sociologists think civilization is simply getting less violent and more civilized, Greenberg said.
That theory was first proposed by German sociologist Norbert Elias in his book The Civilizing Process. Elias wrote that interpersonal violence had been in decline since the Middle Ages, a statement historians now accept.
Elias said that for divine monarchs, like Louis XIV of France, their worth was more measured by their ability at witty badinage and manners than swordsmanship. This more civilized tendency spread to the European middle class and finally, in the nineteenth century, to the working classes.
The decrease also could be partly due to immigration to the city, an influx of people who may be particularly motivated to avoid legal trouble, especially if they are undocumented or because they are determined to make good lives for themselves, Greenberg said.
Then what caused the decline?
"I don't know," Greenberg said.
Andrew Karmen, a sociologist at John Jay College of Criminal Justice in New York agreed.
"People and organizations claimed credit and think they know the reason for the crime drop, but the evidence is insufficient," Karmen said.
Crime also went down across America and in Europe where no one followed the NYPD tactics, said Karmen, who wrote a book on the subject, " New York Murder Mystery: The True Story Behind the Crime Crash of the 1990s."
Karmen agrees that the flow of immigration could be one reason, with the city's population "refreshing" regularly. Another possibility, frequently ignored, is that New York is a college town. The City University of New York system alone enrolls 250,000 undergraduates and they are a substantial—and generally peaceful—portion of the young population.
Karmen said solving the mystery is important.
"If we don't know why the crime rate went down, we won't know what to do when it goes back up," Karmen said.
Joel Shurkin is a freelance writer based in Baltimore. He is the author of nine books on science and the history of science, and has taught science journalism at Stanford University, UC Santa Cruz and the University of Alaska Fairbanks.