Beyond the tip of the iceberg? Exploring Characteristics of the Online Public with Digital Trace Data

Who constitutes the online public, the citizens engaging with political con- tent online? The digital extension of the public arena challenges conventional approaches examining public discourse. Besides mapping the political online ecosystem beyond news outlets, a crucial factor for understanding the on- line public discourse are the individuals involved. Using web tracking data in combination with survey data, we map out who engages with political content across various arenas of the complex political online ecosystem in Germany. We find that people with especially high political knowledge en- gage with political information online. We do not find evidence for strong selection along other demographic, attitudinal, and political variables but instead observe large overlaps among the online public. However, people with rather extreme political views tend to engage more with platforms that enable political expression and discussion than people with more mainstream political views. This finding highlights differences between active and pas- sive political internet use and has implications for the inferences drawn from social media data that usually reflects a - likely skewed - tip of the iceberg.