America had reached its all-time high in crime rates in 1990. From the crack-cocaine epidemic to murder rates being higher than ever. The crime was only predicted to rise despite national efforts. Although by 1994 crime started to decrease, and has ever since. Explaining why the almost sudden change in crime was nearly impossible until recent studies found a link between a law passed in 1978 and the downward trend of crime in the 2000s

The crime peak in the 1990s has been building up since the early seventies. Violent crime rates were through the roof, the crack-cocaine epidemic only spiking the rates to all-time highs. Yet, within the next decade, the crime rates dropped 42%.

An article studying the dramatic decline in crime for the past two decades has presented a couple of theories: A boost in employment, a decrease in alcohol consumption, high incarceration rates, and surprisingly: the decline in lead consumption.

The decline in unemployment may have been a factor of a decrease in crime, with more abundance in money the less incentive of crime. The Brennen Center for Justice estimates that 0-5 percent of the decline in crime can be attributed to lower unemployment rates. But income growth was given a 5-10 percent attribution to declining rates in crime.

Alcohol consumption correlates with three main areas of crime: rape, aggravated assault, and some areas of theft. From 1990-2000 Americans drank slightly less beer, but enough to attribute 7.5% of crime decrease to less alcohol consumption.

America is number one in incarceration worldwide, many people see this as an obvious reason for the steep decline in crime. Without criminals, there is no crime, but it was stated that it had nearly no effect because statistically offenders age out of crime, and the lengthy sentences do little to prevent crime.

56% of the decline of crime was attributed to the lower consumption of lead. In the clean air act of 1970 lead was removed from gasoline and since the crime rates have corresponded perfectly with the change. The reason this was the most profound theory is that children not affected by lead, born in 1970, would commit fewer crimes in their 20s, or the 1990s. This correlation wasn’t only nationwide but international.

Now how does lead consumption affect criminal behavior? Lead has been known to cause socially aggressive behavior, that and impulsivity. It’s the perfect mix for violent crime and petty theft. Lead has also been shown to cause ADHD in children, symptoms being impulsivity as well. In higher amounts, lead can even cause lower IQs. Lead is most notable to cause externalizing aggressive behavior like bullying and violence.

In 1978 lead became illegal for use in America, the theory is that in 1978 children that were born would consume less lead so in their teenage to early adulthood they would commit less crime. This theory was proven correct in multiple studies in the past couple of years. This has also created a new link between poorer areas and crime rates, unfortunately, there are still trace amounts of lead in waterlines across America.