Is Music More or Less Dance-y?

What makes a song danceable? And what does it mean for "danceability" to change over time? People were fox-trotting, jitter-buggings, and tango-ing long before the days of algorithmic party playlists, Bruno Mars, and EDM. It's not like people in the late 1950s abstained from dance because they were waiting for Outkast or Lil Baby. No, they listened to Bobby Darin and Elvis and thought, "Wow, I love dancing to this sufficiently danceable music."

And yet, according to Spotify's "danceability" scoring, popular music has become increasingly danceable over time:

So what is driving this purported uptick? A few theories:

1. Recency Bias in Spotify's Scoring Algorithm: Popular dance music typically exists within distinct cultural epochs (50s Doo-Wop, 60s Motown, 70s Disco, etc.). Would you expect the same playlist at a wedding and a nightclub? No. Nightclubs cater to younger audiences and promote dance by playing the latest electronic music, hip-hop, and rap. On the other hand, weddings serve a broad age range, often catering to older demographics by playing from a list of well-worn classics (like "September" by Earth, Wind, and Fire). Spotify's song scoring may favor newer music that reflects contemporary dance trends.
2. The Importance of Live Music: The digitization of music distribution offers consumers content abundance in return for a tidy and affordable subscription fee. In response, music acts have shifted their profit centers from record sales to live performances. And what do people like to do at music shows? Dance (while wearing a flower crown)! Hip-hop, rap, and electronic music are cheap to produce and easy to promote, thus fetching increased attention from record labels and concert promoters.       
3. Industrialization of Music Production: In 1998, Cher's mega-hit single "Believe" made prominent (and ear-punishing) use of auto-tune. This new-fangled computerized effect became a focal point of the song's appeal and served as a watershed moment for the mechanization of music production. Since then, audio engineering has become increasingly computerized, with major labels adopting digital workflows, while programs like Logic and GarageBand have democratized production for aspiring musicians. Artists have gradually converged on a homogenized sound for hip-hop, rap, and electronic music, utilizing technology to produce optimally danceable beats.
4. The Rise of Hip-hop and Rap: Sorting through our artists repeatedly featured on the Billboard Charts, it appears Spotify's algorithm categorizes modern hip-hop and rap as the most danceable music genres: 

Meanwhile, Spotify’s feature rankings classify traditional pop (from the 1950s and 1960s) and soft rock as the least danceable music format.