Before revision:  We then perform a pair of user studies with 4357 unique users (recruited from Google Ads and Amazon Mechanical Turk) in which we observe how users interact with different opt-out mechanisms and evaluate how the implementation choices we observed---exclusive use of links, prevalent nudging, and indirect mechanisms---affect the rate at which users exercise their right to opt-out of sale.
After revision:  We then perform a pair of user studies with 4357 unique users (recruited from Google Ads and Amazon Mechanical Turk) in which we observe how users interact with different opt-out mechanisms and evaluate how the implementation choices we observed -- exclusive use of links, prevalent nudging, and indirect mechanisms---affect the rate at which users exercise their right to opt-out of sale.