Correlates neatly with the decline in lead in the environment, and is related.
http://www.motherjones.com/environment/2013/01/lead-crime-link-gasoline
The reason I've most often heard for the declining crime rate is "abortion of unwanted babies!!", and while that argument seems to make sense, it starts to fall apart when you realize it does not answer the necessary OTHER question, namely, "what caused crime to go up in the first place?" This explanation does, though that does not guarantee that it is correct.
http://www.motherjones.com/environment/2013/01/lead-crime-link-gasoline
The reason I've most often heard for the declining crime rate is "abortion of unwanted babies!!", and while that argument seems to make sense, it starts to fall apart when you realize it does not answer the necessary OTHER question, namely, "what caused crime to go up in the first place?" This explanation does, though that does not guarantee that it is correct.