he US study team looked at lyrics of more than 6,000 songs from Billboard Hot 100 in each year.
These are the most popular songs in the US each year as chosen by music fans.
In the past songs were ranked mainly by record sales, radio and jukebox plays, but more recently it is based on other popularity indicators such as streaming and social media to reflect changes in music consumption.
The analysis showed the expression of anger in popular music lyrics has increased gradually over time.
Study co-author Lior Shamir, of Lawrence Technological University in Michigan, said: 'The change in lyrics sentiments does not necessarily reflect what the musicians and songwriters wanted to express, but is more related to what music consumers wanted to listen to in each year.'