Not sure if this response will be acceptable for this subreddit, as it is more along the lines of a scientific explanation than a purely historical one, but there are a few theories as to why there was such a precipitous drop in crime during that period. The ubiquity and subsequent removal of environmental lead, mostly in the form of gasoline and paint, is commonly theorized to be a major contributing factor to both the preceding rise and subsequent fall of crime during that period, with many different journal articles showing evidence of a correlation existing. This article from Juvenile Justice Information Exchange Organization does a good job of summarizing much of it. That lead is known to cause structural changes to a developing brain is well known, and we also know that environmental lead levels have decreased since changes in legislation required the removal from gasoline and paints. That decline in lead lines up with a delayed decline in the rate of crime, which is what you'd expect if this hypothesis were true.

There are of course other theories, like the one made popular by Steven Levitts book Freakanomics which focuses on the correlation between abortion and the subsequent decline in crime, showing that those states which legalized abortion earlier showed earlier declines in crime than those whose laws were changed by the Roe v. Wade ruling. The theory hinges on the idea that those children aborted are more likely to be born to less ideal familial situations and therefore are more likely to commit crimes, and aborting them allows for that crime to not occur.

Both of these are just theories based on correlations, but both are fairly well supported by the evidence.

A large part of the crime spike was due to the "crack epidemic." Gangs started killing each other over turf wars in an effort to control the new drug as it hit the market. There is lots of criminological research on this topic. The drug and its use eventually went down as people learned of its dangers, which led to these gangland crime rates falling. Source: Crime Readings by Robert Crutchfield link to relevant chapter

Edit 2: Relevant passage - "Within any given locale, the increased demand for crack led to the extensive recruitment of young minority males to serve as drug dealers. Violence typically surrounds drug markets, and thus new recruits acquired firearms to fend off other drug dealers...Interpersonal disputes become more lethal, and the homicide rate rose. Subsequently, the number of crack users dropped off, beginning in the early 1990s in some cities. This let up on the pressure to recruit more drug dealers and brought some stability to drug markets. Accordingly, as the crack epidemic began to subside, homicide rates started to fall."

Edit: Yes, go ahead and down vote me. I actually cited a publication by a prominent sociological researcher. This theory holds a tremendous amount of weight and has actual evidence unlike the guff you always hear about lead.

Can we treat official crime rates with a little more scepticism? The British Crime Survey, for example, estimates that only one in four crimes is ever reported. So what may seem like dip or a jump in crime rates could have more to do with changes in law enforcement or patterns of reporting than any change in criminal behaviour.

What's more, the definition of what a crime is evolves over time. For example, E.P. Thompson has shown that customary activities such as hunting and cutting timber were criminalized over the course of the 17th and 18th centuries as owners of landed estates became increasingly interested in protecting their property rights.

Peter Linebaugh, meanwhile, has shown that London dockworkers customarily took pieces of timber as a supplement to their wages - until this practice was deemed to be criminal in the 18th century.

So something that could be considered a "custom" in one context becomes a "crime" in another. It might be counted as an increase in crime rates, but it also might have to do with changes in the definitions of property or the passage of new criminal laws.

And, when it comes to the United States, the criminal justice system has often been used to address social problems that other countries would treat through social welfare. Ta-Nehisi Coates has discussed this in a recent article that deals with the correlation between race, poverty, family structure, and mass incarceration.

Not saying that crime statistics aren't reliable, or that they're all subjective - obviously, a murder is a murder no matter how you count it - but I'm not certain you should take them at face value either.

Question: could any of the rise and fall be simply corolated with the age of babyboomers?