had often concluded that personal canvassing produced far higher voter turnout rates, such as 9.8–12.8%. While most experiments have been conducted in the US, recent studies have found similar or somewhat smaller effects in Europe. The guide to grassroots elections Get Out the Vote determined that GOTV efforts averaged one vote every 15 door knocks by volunteers ($31 dollars per vote), 35 phone calls by volunteers ($35 dollars per vote), or 273 pieces of nonpartisan direct mail ($91 dollars per vote, no effect from partisan direct mail). They note that campaigns which experiment carefully can do better than these averages. Campaigns can raise turnout up to 8 percentage points with direct mail which tells neighbors when other neighbors have voted and promises to mail an update after the election, though people complain when they have no way to opt in or out of notification. Other studies have found that GOTV methods contribute little to none to voter turnout. One field experiment found that GOTV phone calls were largely ineffective, and that ease of access to polling locations had the largest impact on voter turnout. There is also the argument that GOTV targets a more affluent demographic, which is already more likely to vote. Less politically engaged demographic and socioeconomic groups are sometimes neglected in GOTV efforts. GOTV is often most effective when potential voters are told to do so "because others will ask." Voters will then go to the polls as a means of fulfilling perceived societal expectations. Paradoxically, informing voters that turnout is expecting to be high was found to increase actual voter turnout, while predicting lower turnouts actually resulted in less voters. In 2004, Rock the Vote paid to run TV ads aimed at young voters, on a random sample of small cable systems where they could measure the effects. Turnout was three percentage points higher among 18- to 19-year-olds in these sample areas than in the control group covered by other similar small cable systems; there was less effect above age 22. In November 2012 and 2013, Rock the Vote experimented with Facebook ads to encourage voter turnout by telling people the number of days remaining until the election and which of their friends "liked" the countdown. The ads were shown to over 400,000 adults, randomly selected from a base over 800,000. Rock the Vote had helped many of them register. The ads did not increase turnout