I saw an interesting presentation by Helen Margetts from the Oxford Internet Institute at Southampton last month. Her research suggests a threshold effect for political participation. Under her experimental conditions, people were statistically significantly more likely to participate politically (in this case, to sign a petition) if they could see that more than one million other people had signed. There was no effect on participation for additional signatories over this level. This suggests a threshold, rather than a bandwagon effect. If people were more likely to jump on a moving bandwagon, the odds of participating should depend on the number of signatories full stop (rather than just depending on whether the one million threshold had been reached).
Experiments always raise questions, of course. Do the conditions mimic the real world? Does observing people this closely change what they do? Helen’s question, though, was: “what does one million mean?” Is it just a big number? Is it what the media thinks is a big number? Can we call a petition with a million signatories a success?