Well, almost predictable. The changes are consistent and occur at a predictable rate but because they are random, no one can predict exactly which new fashions will replace the old ones.

Huh?

“It’s like American Idol,” said Dr Alex Bentley, a Lecturer in the Anthropology Department at Durham University. “We can predict the steady production of new winners from programme to programme, but the randomness means we can’t forecast the particular winners themselves.”

The research adds further weight to previous work by researchers, which challenged beliefs that our fashion choices are independent, rational decisions, showing that we are generally copycats when it comes to popular culture. New ideas can become highly popular by random copying alone, and be replaced over time as the next generation of innovations are copied.

The researchers say innovation is what actually drives fashion change – the more innovators per capita, the faster the turnover. “Innovators are the cool ones who ‘pump’ new fashions into our world,” Dr Bentley explains. “Most are ignored, but some get copied.” Viral marketing professionals grasp this, says Dr Bentley, as they identify a tiny minority of true innovators among a vast majority of copiers.

The trick is, say the researchers, is to find the innovator with the next big hit. Celebrities, for example, get copied much more than random copying would predict. Dr Bentley said: “David Beckham in the early 2000’s was an innovator with his haircuts but it’s change itself that is actually in demand, more or less regardless of content. Madonna knows this –staying on top for two decades by changing her image constantly.”

The researchers say the steady turnover discovered under the random copying model could be used to predict turnover rates on bestseller lists, as well as distinguish copying from other forms of collective behaviour.

Dr Bentley, Principal Investigator at the AHRC Centre for the Evolution of Cultural Diversity, collaborated with colleagues at California State University, Western Carolina University and Indiana University in the US. They looked at the Billboard Top 200 chart and found that it turned over at a constant average rate for 30 years, from the 1950s to the 1980s. The number of albums entering and exiting the chart varied from day to day and month to month, but overall the average turnover was 5.6% per month for the full 30-year period. They discovered a similar consistency in turnover for the top baby names and dog breeds.

This real-world data was matched by computer simulations of a random copying model, in which with hundreds or thousands of individuals copy each other from one instant to the next, with a small proportion of innovators (2% or less). During the simulation, they kept track of the Top 40, Top 100 most popular ‘fashions’ and monitored their turnover. The model predicted continuous and regular turnover, consistent with the real-world data from the charts of baby names, music and dog breeds.

How quickly a list will change depends on the size of the list – a Top 100 changes proportionally faster than a Top 40 – but, surprisingly, the size of the population does not have an impact, the research found. Although a larger population means more new ideas, it also means more competition to reach the top, and the two balance each other out: the turnover on bestseller lists remains steady as population size changes.

Random copying, however, does not lead to a ‘rational’ collective decision, which is fine for fashions, but undesirable for public policy, say the researchers. In most situations, such as voting or investing, it is best for society if people make their own rational informed choices. “When political agendas are constantly changing, it’s a sign that politicians are copying each other rather than thinking for themselves,” Dr Bentley said.

Written from a news release by Durham University.