Recent research in economics, psychology, and political science describes the 'bandwagon effect' - or alternatively 'contagion effect' - as a general cultural phenomenon or in which the rate at which the spread of ideas, behaviour, and trends more generally, rises with the rate of others adopting the trend. A 2020 paper in the Journal of Political Economy, thus describes the effect as the capacity to incentivize investment by itself.

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The phrase 'jump on the bandwagon' is typically used in a derogatory fashion to indicate that someone is following a trend without actually having made a rational evaluation of the idea or behaviour itself. It is thus merely the success of the trend that leads to its further success.

In other words: the probability of someone adopting the idea or behaviour rises with the share (or perceived share) of others in a population adopting the trend.

The phrase itself originates in American 19th-century , when Dan Rice, a famous circus clown, ran for various political offices (including the Presidency of the United States). He eventually campaigned for Zachary Taylor, the 12th President of the United States with a bandwagon and music, thus leading to other campaigning politicians imitating the practice and subsequently the now-popular expression: 'to jump on the bandwagon'.

The examples for the effect are manifold:

Elections in which an initially equal field of candidates is suddenly dominated by a candidate who has received a minor victory. (A recent example is Joe Biden, who after being written off by many in the 2020 Democratic presidential race suddenly came to dominate the field after a victory in the South Carolina Democratic Primary.) Cultural trends that suddenly get imitated by many, seemingly for the sole reason that the practice has become popular. (Think of the ALS ice bucket challenge or the popularity of a particular hairstyle such as the 'undercut'.) Similarly, collective behaviour that, after reaching an initial tipping point, seems to be imitated by everyone to the point that it has disastrous effects. (Think of the irrational mass toilet paper sales in Australia in response to the epidemic, to the point that many stores have run out of toilet paper entirely.) Competing individuals or teams in sports that suddenly gain a huge following after an initial (often surprising) victory. This effect is also related to the idea of an 'underdog effect'.

Economists have explained the effect as follows: because the demand for 'bandwagon-goods' seems to increase with greater demand, they have interpreted the effect as a preference that increases in strength correspondingly to how many people demand or buy the good, or at least how many the agent thinks do so. It is an odd result that seems to conflict with standard economic theory, where the sole criterion is the price of a good and an agent's preference.

Yet, information theory has done a great deal to understand the effect further. While we are very social creatures and tend to imitate the people close to us, there might be an underlying rationale in the sense that we discover or infer an underlying reason for a behaviour that is suddenly taken up by many around us. Consider the thought experiment of leaving a store only to find all the people on the streets running in a particular direction. Without thinking, it might be best to just follow them, for there could be a danger looming in the opposite direction. Evolutionarily this makes a lot of sense for we might have to run away from predators or natural disasters such as a fire that is engulfing the area. Indeed, even many species of animals seem to be subject to this - imitating the behaviours of others.

Another potential human example would be two empty Indian restaurants with big windows next to each other. We might have no initial reason to prefer one over the other. But now we see a customer entering one of them. This might reveal information about the quality of the restaurant and hence we would follow. Yet, this need not always be the case. The first customer may very well have chosen randomly, and thus picked an objectively worse restaurant. Yet, others might follow his lead - thus leading to the success of the objectively worse restaurant. This is why it is called the bandwagon effect, a potential bias that can lead to surprising collective behaviour that need not always be beneficial or rational.

You might, therefore, want to think twice before following the behaviour of others, but don't be surprised if you and others continue to 'blindly' do so.

Click here for an article on Joe Biden's victory and the Bandwagon effect.

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