How deeply did lead's toxicity affect society? Well, economist Rick Nevin believes it might just be a major underlying cause of the recent global crime decline.

Nevin studied the criminal histories of nine countries and found that in each case he could link significant crime drops with that country's campaign to eliminate childhood lead poisoning. In his own words, "65 to 90 percent or more of the substantial variation in violent crime in all these countries was explained by lead." You could say that the timing was just coincidence, but each country Nevin studied conducted those campaigns at different points in time, and in every case, 20 years after lead poisoning rates fell, crime started to fall. Another study in 1990 showed that U.S. counties with high lead levels had four times the murder rate of counties with low lead exposure.

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Shotgun victims are also very likely to have high lead exposure.

Now, as with every entry on this list, we'll never know for sure how true this was -- you could just as easily say that the type of country or era that is advanced enough to successfully deal with environmental problems is also capable of fighting crime. Still, it makes us wonder what stuff we're all being exposed to right now that will turn out to have been making us crazy. We're imagining a future earth in chaos, roving bands of savages driven mad by a decade of iPhone fumes.

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If not the iPhones themselves.

You have to keep in mind that plummeting crime rates are falling off from highs reached thanks to the crack epidemic -- this sudden invasion of an impossibly addictive yet dirt cheap drug caused homicide, robbery and drug arrests to explode in the mid-'80s. But then the rates suddenly started plummeting in 1991, and kept going down. While that's good news for everyone, it's also kind of baffling. Crack is as addictive as ... well, crack. Wouldn't it just keep spreading like a disease until every inner city neighborhood is full of addicts? What stopped it?

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Bears?

Apparently, crackheads did. That is, the fear of becoming one. A pair of researchers in New York say that crack fell out of popularity because its effects on people are freaking terrifying, even to other drug users. Pot brings up the pleasant image of comfy couches and junk food. Alcohol calls up crowded bars and raucous house parties. You can even convince yourself that heroin and powder cocaine are glamorous, thanks to their use among rich rock stars and actors. But crack? It pretty much just makes you think of constantly broke, malnourished junkies offering oral sex to their dealer in exchange for one more hit.

thegooddrugsguide

So, the idea is that a lot of the potential market for the drug saw how rapidly it turned people into shrunken zombies, and backed slowly away in horror. They then switched back to pot, which in addition to not turning you into a crackhead also doesn't spawn the same kind of brutal turf wars and desperate, violent users. When the crack left, so did the attendant handguns and robberies that served to feed all those crack habits. Inner city crime plunged and snack food industry profits soared.

"But wait," you say. "What about meth? I've seen Breaking Bad, there are more people doing drugs now than ever! And killing each other for it!"

"And it's freaking awesome!"

Well, the thing is ...

It's perfectly natural to think "More drugs = more crime." Illegal drugs are, by definition, sold by criminals. More drugs equals more criminals, which equals more crime, right? But it's not that simple.

People kill each other over drugs for the same reason they kill each other over oil, or diamonds: because they're worth a huge amount of money. In 1988, the cocaine trade was worth an estimated $140 billion. If that doesn't drive home how blow-crazy America was during the late '80s, we'll put it another way: Cocaine was worth 2 percent of the entire U.S. GDP. And only, like, a third of that can be pinned on Robin Williams. At around the same time, America's murder rate reached its highest level in recorded history -- and almost none of that can be blamed on Robin Williams.

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Fashion is always the first victim.

But when the mid-'90s rolled around, coke dropped in value faster than hammer pants. By 1994, the price of blow was at its lowest point ever and, holy s**t would you look at that, the murder rate dropped by 50 percent as well.

This baffled the DEA, who'd been busting coke dealers left and right in the hopes of making the drug less accessible (and thus more expensive). But it appears that all they actually succeeded in doing was forcing drug lords to smuggle smarter and diversify. Then in came meth, which anybody can make in their garage for a few bucks, and a new jump in popularity for pain pills. And, if high school economics taught us anything besides how to sleep with our eyes open, it's that introducing more choice into a market lowers prices.

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"Keep three degrees of separation between you and the product, and never carry more than you can swallow."

That means that, suddenly, the profit margins for street-level dealers really started to ... blow. So-called "minimum wage dealers" made as little as 50 bucks a month, which probably isn't enough to shoot someone over, and sure as hell isn't worth taking a bullet over. Turf wars disappeared, violent crime rates dropped, poor cocaine found itself relegated to the bargain bin and addicts suddenly had extra cash to spend on ... well, probably more drugs.

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"My long term goals involve finding somewhere to sleep without being peed on."

This does not, obviously, mean that the key to utopia is to create a world where the very streets are paved with meth. It just appears that such a world would feature fewer drive-by shootings.

For as long as cities have been a thing, groups of disaffected youngsters have banded together to murder other groups of disaffected youngsters. Gangs are responsible for a lot of violence and property crime, is what we're saying. So when we hear statistics reporting a 10 percent drop in violent crime nationwide or a 23 percent drop in LA homicides, it's only natural to assume that there are fewer gang members on the streets. But in reality, gang numbers have risen to an estimated 1.4 million gangsters in 33,000 distinct gangs as of 2011.

How does that work? Isn't street crime the entire point of having a "gang"? Are these new gangs making their money by having dance-offs like West Side Story?

Well, they're still committing crimes -- they're just not the kind that require shanking a dude. Today's gangs have apparently discovered that the digital age offers crime that is simultaneously less risky and more profitable than pushing dope and capping asses. While crimes like counterfeiting, bank/credit card fraud and identity theft have spiked over the last several years, gang-related violent crime continues to fall from LA to Raleigh and from Santa Barbara to San Castle. Los Angeles civil rights lawyer Connie Rice says gang-related cybercrime rose by 1,500 percent in LA from 2009 to 2010 alone. It's not exactly a win-win, but it sure as hell beats drive-by shootings or ganking people because they wore the wrong color shirt in the wrong neighborhood.

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"That's twice in one week you've worn sweatpants. Now you don't get to eat lunch with us."

The money is a big factor in this, but the disparity in punishments matters as well: Armed robbery will land you seven years in prison and maybe get you shot in the face, while you can make just as much cash stealing someone's identity and only do a few months of time. Plus, no one can shoot you in the face over the Internet (not until the U.S. Patent Office finally approves our application).

The video conference helped.

And since 95 percent of financial crimes go unreported, your average geeky gangster has pretty goddamn good odds of getting away with it.

You don't have to look far to find people claiming that illegal immigrants are wantonly murdering Americans or that they are violent terrorists. But studies have shown that non-citizens born in Mexico but living in America are eight times less likely than male U.S. citizens to be incarcerated. Likewise, the American cities that saw the greatest increase in their illegal immigrant populations from 1990 to 2000 also saw the greatest drops in robbery and homicide.

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"Hey, this place looks real nice. Let's try not to f**k it up."

Remember that massive drop in New York City crime rates that Rudy Giuliani liked to take single-handed credit for? Yeah, turns out it might have been in no small part thanks to the steady rise in the immigrant population of the city. Since 1994, America's illegal population has doubled, while violent crime fell 34 percent and property crime fell 26 percent. Eight of the 10 safest large cities in the United States also boast high immigrant populations.

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We're crediting Giuliani with that. Who wouldn't want to live in the same country as this adorable little face?

There is almost no way to find out why this is, and this subject is such a political hot button issue that there is almost no way to speculate without your guess being grossly offensive to someone. And guessing is all it is -- some critics say the stats are skewed because the crimes are under-reported, since they tend to happen in neighborhoods full of undocumented immigrants who can't go to the police without fear of getting deported themselves. Or, maybe fear of deportation is motivation enough to just not commit crimes at all. Less cynical types say it's a matter of immigrant neighborhoods being more tightly knit, everybody keeping an eye out, the way we imagine everybody did it in the 1950s. Hell, maybe new immigrants just have a sense of optimism that too many Adam Sandler movies and Kardashian spin-offs have robbed born-and-bred Americans of.

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"Come to America, Mavis. This new Shakespearean vulgarity is just the worst."

And if you think those stats are impossible to talk about without triggering a political shitstorm, go tell your neighbors that the crime drop might be partially due to ...

Let's just go ahead and rip this Band-Aid right on off: Economists John Donohue and Steven Levitt (aka the Freakonomics guy) make a compelling case that our massive 20-year plunge in violent crime is partly due to legalized abortion. They note that our crime rate began its decline precisely 18 years after Roe v. Wade -- in other words, right around the time that all those legally aborted fetuses would have reached prime gangbangin' and liquor store robbin' age. Furthermore, they also noted that the states that experienced the sharpest crime drop in the '90s were the ones that performed the most abortions in the '70s and '80s. Their final conclusion?

"Legalized abortion appears to account for as much as 50 percent of the recent drop in crime."

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Although we're sure our "stop giving guns to babies" initiative helped.

That's right: According to Donohue and Levitt, as much as half of the recent crime rate cliff drop can be attributed to legalized abortion. There are a few theories as to why this might be the case, each more likely to get us yelled at than the last. Essentially, more abortions mean fewer impoverished, teenaged and single mothers, and studies have shown that kids born into those situations are more likely to turn to crime.

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"Your mom's so fat because of a range of socioeconomic disadvantages. I'm sorry, dude."

A bunch of people way smarter than us have come out to both support and slam the theory, and critics make it sound like the proponents are promoting eugenics. But really, even if the conclusions of the study are correct, it doesn't need to change your opinion on abortion. If you think abortion is murder, then "the kid might have grown up to steal your car" argument obviously doesn't suddenly make it OK. Conversely, if you're in favor of legalized abortion, it's because you believe in a woman having that choice, not because you want to exterminate all of society's undesirables in the womb.

See? There's nothing to get upset about at all. We got all worked up over nothing.

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Please leave all ire in the comments while we work on that Internet shooting patent.

Robert Evans oversees the article captions and the Cracked workshop moderator team. When he isn't doing either of those things, he writes letters to his conservative parents about the economy, illegal immigration and drug law.

For more of what science says about crime, check out 5 Common Crime Fighting Tactics (Statistics Say Don't Work). Or learn about the 5 Ridiculous Attempts at Crime Fighting (That Worked).