In an online experiment, we measure users' interactions with search engines, both in standard configurations and in modified versions with improved labels identifying search engine advertisements. In particular, for a random subset of users, we change "sponsored link" or "ad" labels to instead read "paid advertisement." Relative to users receiving the "sponsored link" or "ad" labels, users receiving the "paid advertisement" label click 23% and 26% fewer advertisements, respectively. Users seeing "paid advertisement" labels also correctly report that they click fewer advertisements, controlling for the number of advertisements they actually click. Results are most pronounced for commercial searches, and for users with low income, low education, and little online experience. We find no evidence that consumers find Google's new "ads" label more informative than the longstanding prior label "sponsored links."