Passive internet tracking (usually through proxy or vpns) is commonly considered a high-precision measure of internet usage. In this paper, we take a look at limitations of that method.
We show that there is a differential bias between computer and mobile device tracking, which can be attributed either to self-selection or measurement errors. Both are worrying.
Two Half-Truths Make a Whole? On Bias in Self-Reports and Tracking Data
Social Science Computer Review. Online First.