Do you remember where you were when you first heard The Sugarhill Gang? “Now what you hear is not a test I'm rapping to the beat And me, the groove and my friends We’re going to try to move your feet.” OK, you kind of remember it? (Laughter) OK, I'm a professor, so here's your quiz. Everybody say “Hotel, motel” -- Audience: "... Holiday Inn." RF: OK, stop that. (Laughter) We can't have that kind of fun, I work at Harvard. (Laughter) I first heard that song -- It's, like, 1985. It was a block party in Daytona Beach, Florida, and people were moving in ways I'd never seen before. Now, I'm not talking about my friend Manman. I'm talking about my grandmother. She was doing stuff I can't unsee. (Laughter) She was like, down in here, and I was like, “Whoa, grandma!” (Laughter) That was 40 years ago. And hip-hop has taken over. It is the most popular music genre in the world, particularly among young people. ... I'm a Peloton addict. And I went to New York for the live ride. And I'm in the studio ... we’re 35 minutes in -- I was thinking, “How do you simulate the bicycle?” Here we go. I was 35 minutes in, I peeped the person next to me, and her handle was RideorDie2000. And they get us up out of our saddles, 35 minutes in ... and, on beat, she gets up out of the saddle, she starts screaming, and pounding the handlebars, "Kill, kill, kill, Murder, murder, murder" (Laughter) Scared the crap out of me. (Laughter) In that moment, I realized two things. Number one: hip-hop done made it, y'all. (Laughter) There is a middle-aged white woman from Charleston, South Carolina, talking about murdering somebody in public. (Laughter) And number two: According to some of y'all, because of those lyrics, she's likely to murder someone this afternoon. (Laughter) And I'm selfish. I want to know who. (Laughter)

Hip-hop is everywhere. I collected data, we collected data, a team of us collected data on every radio station in America. And for every radio station, we know the genre of the songs. So as this interactive graph gets more red, that is the spread of hip-hop across every county in America. Now to collect the data, first we went and got literally every radio handle. And for every radio handle, we have the broadcast frequency and range from each one of them. And then, we have the genre. And then, for some of the radio stations, we actually have the playlists that were on the radio. And for those playlists, of course, we have the songs. We analyzed every lyric that has been played on many radio stations in America. Now it took a team of us to do this, and with the advances in AI, we made more progress in the last six months than we made in the first 10 years. Now you can imagine having research assistants sit and listen to a bunch of hip-hop and score it all day long. AI has been much, much more helpful.

This shows you we've looked at the evolution of the types of hip-hop played on the radio over the last 40 years. The bottom is what I call alternative, or what they call alternative or experimental hip-hop. Think OutKast. It's a small portion, but this is the kind of hip-hop that pushes boundaries. The second, the yellow, is conscious or lyrical hip-hop. Think Kendrick Lamar, who was brilliant enough to win a Pulitzer Prize for his lyrics. That's the next sliver. The big part in the middle is mainstream hip-hop, the type that's played on the radio most of the time. Think Jay-Z or -- I'm a little older -- Run-DMC. Now at the top, that’s where the controversy is. That is street rap -- think Dr. Dre, Tupac. ... We trained the AI to grade each song in terms of how misogynistic it was, how violent the content is, how profane the language is and the drug references. Over the last 40 years, hip-hop music has gotten five times more misogynistic, five times more violent, five times more profane ... but only two-and-a-half times as many drug references. ... In 1993, I was 15 years old, and I drove to a prison to visit my father. ... And MC Eiht came across the speakers, and he said, "A fucked-up childhood is why the way I am Has got me in the state where I don’t give a damn Somebody help me But no, y’all don’t hear me though I guess I’ll be another victim of the ghetto Now that would score high on profanity and violence. But in that moment, it scored high on comfort.

And we can relate those, and we do, to 40 different variables that measure social and economic progress: things like teen pregnancy, things like unemployment, income, crime. And here's what the evidence shows. On every dimension, all 40 of them, we find zero evidence that hip-hop has a negative effect on any outcomes. (Applause) What this shows you on the vertical axis is the homicide rate, and on the horizontal axis is exposure to hip-hop. And what you see, statistically, is no relationship, but, if anything, slightly downward-sloping, which means exposure to hip-hop made things, if anything, better, not worse. ... I was told, my entire life, that hip-hop causes inequality. Well if you actually process hundreds of thousands of songs and relate it to outcomes, the data actually suggests the opposite, that inequality causes hip-hop. (Cheers and applause) So the solution is simple. If we want gentler lyrics, how about we work together to change the social conditions that produce the lyrics? Thank you. (Cheers and applause) And we can dance. It's not going to hurt you. (Cheers and applause)