25 years ago this was kind of a rough Street and you definitely think twice about walking it alone at night but since the 90s crime in San Francisco has gone way down and not to San Francisco or California but across the entire country nationwide the crime rate is almost half of what it was in 1990 one thing is no one knows exactly how or why it has happened most experts say it's not one single thing but a combination of factors here are just three plausible explanations first mass incarceration we've been jailing more Americans at record rates and crime has gone down and you might think well that makes sense you're locking up more criminals so of course there's less crime out there on the streets happening and some extent you're right the Brennan Center for Justice says that mass incarceration accounts for a slight drop in property crime since 1990 things like robbing houses stealing cars and so on but the Brennan Center says you can actually attribute the drop in violent crime to mass incarceration for a few reasons one is that increased incarceration has meant that more nonviolent offenders have gotten locked up which obviously doesn't have a big impact on violent crime and the Brenden center's numbers show that increase incarceration doesn't even necessarily deter crime which might help explain why in some large states like California the prison population has decreased and crime has still gone down so obviously jailing more and more people doesn't explain why crime has gone down another theory new police strategies in the 90s increased funding put more police officers on the streets and some argue that those numbers helped reduce crime but others say the evidence isn't totally consistent in San Diego for example there were no extra police officers and yet crime still went down there then there's police strategies like broken windows which targets low-level crimes and misdemeanors things like selling loose cigarettes on the street or smoking weed out in the open the jury's still out on how big of a role that helped play and reduce crime finally the introduction of something called CompStat definitely seems to have had an effect ComStat basically allowed police officers to measure crime stats and target specific neighborhoods and crime for the first time starting in the 90s no matter what it's likely that police did play a role in the crime drop but that's not the only explanation the third big factor the economy the idea is that when more people have jobs there's less crime as unemployment went down in the 90s crime also went down and as unemployment went up in the 2000 crime also saw a small increase it gets complicated though when you consider that the recession in 2008 didn't actually lead to an increase in crime so what about income as per-capita income grew in the 90s crime decreased in fact the higher the average income in the state the lower the crime rate but more money could mean more incentive for criminals like in neighborhoods that have a big economic disparity so obviously the crime drop is pretty hard to explain and there's a whole bunch of other theories people drinking less that our access to abortion decreased crack use Obama mania making folks feel good in 2008 our aging population and less exposure to lay yep lead so what do you think is behind the drop in crime let us know back in the 1960s our incarceration rates were the same as Europe's and if you think there's just more crime here that's not true either our crime