Musicians are singing a lot more about sex and a lot less about love now than they did in the 1960s, found data artist Nickolay Lamm when he analyzed the lyrics of every song that has appeared on the Billboard Hot 100 singles chart since 1960.

“Money,” “weed,” “body,” “foul,” “hate” and “kill” also pop up more often now than they used to, while “lonely,” “sad,” “heart” and “I love you” were more popular in songs in the past, according to Lamm’s analysis.

Lamm created a series of charts based on his analysis, and they’re fascinating.

Here’s how to decipher the charts, according to Lamm.

The horizontal axis is the year of the song's release and the y-axis is the song's popularity according to Billboard Year-End Hot 100 singles. Each cell represents a song. The more red a song is, the more often that particular word appears in the song. For example, if a song has 5 "love" words and a total of 100 words in the entire song, that song is assigned a 5 percent value and a particular shade of red. The higher the percent, the darker the shade of red.

Take a look:

Photo: Nickolay Lamm

Photo: Nickolay Lamm

Photo: Nickolay Lamm

Photo: Nickolay Lamm

Photo: Nickolay Lamm

Photo: Nickolay Lamm

Photo: Nickolay Lamm

Photo: Nickolay Lamm

Photo: Nickolay Lamm

Photo: Nickolay Lamm

Photo: Nickolay Lamm

Photo: Nickolay Lamm

Photo: Nickolay Lamm

Photo: Nickolay Lamm

Photo: Nickolay Lamm

Photo: Nickolay Lamm Photo: Nickolay Lamm

Photo: Nickolay Lamm

Photo: Nickolay Lamm

Photo: Nickolay Lamm