Linguists and psychologists have been using the content of messages on Twitter to learn more about our society -- from gender and age trends to politics. Now, a new study by computer scientists at the University of Pennsylvania has found that the behavior of Twitter users also correlate with their income levels.

The team of researchers, led by Daniel Preotiuc-Pietro of Penn’s Positive Psychology Center, analyzed more than 10 million posts of 5,191 publicly available Twitter user profiles. The data was collected in August 2014 and the most recent 3,000 posts from each person were used.

To calculate income level, the researchers* used England’s job code system to sort the self-described occupations provided in the profiles and assign a representative, mean income for each code. That data was then used to identify links to a user’s wealth and their tweeting behavior.

The researchers evaluated how high- and low-income users use Twitter for different purposes. High income users use it more for disseminating information and had more followers. Lower-income users use it more for social reasons, including sharing links in their tweets.

As you can see in this chart, people earning an average of 45,000 pounds ($69,000) had far more Twitter followers than people making much less.

Although the reason behind the trend is unclear, it is also interesting that Twitter users making more money retweeted more content than Twitter users making less money. And lesser-paid tweeters liked to include links more often in their postings.

The researchers also analyzed the content of the messages. Feelings of fear and anger inferred in tweets of high income users stood out in particular.

*Other researchers included Svitlana Volkova of Johns Hopkins University, Yoram Bachrach of Microsoft Research and Vasileios Lampos and Nikolaos Aletras of University College London.