The value of GOTV is unclear, but a well-organized effort can gain a candidate as much as nine percentage points in campaigns in the United States. In terms of mobilization, studies have found that door-to-door canvassing increases turnout among the contacted households with approximately 4.3 percentage points, according to experts Alan Gerber and Gregory Huber in 2016 while a 2013 study of 71 canvasses including many that targeted low propensity voters found turnout increased by 2–3 percentage points. Even earlier, analysts 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.