http://www.straitstimes.com/Latest%2BNews/Tech%2B%2526%2BScience/STIStory_244627.html
June 5, 2008
Tracking the movements of 100,000 people over six months through
cell phone use, the researchers discovered that highly variable
individual travel patterns collapsed into a single mathematical
formula of probability.
'Despite the diversity of their travel histories, human follow
simple reproducible patterns,' said co-author Cesar Hidalgo of
Northeastern University in Boston.
Truly creatures of habit, most people migrate consistently to
the same handful of spots, with occasional 'long hops' to more
distant locations, said the study, published in the British journal
Nature.
'Less than three per cent of people move regularly over more
than 170km,' Mr Hidalgo said.
Predicting the movement of people during an epidemic, after an
earthquake or in a traffic jam following a big football match has
always been something of a guessing game for scientists, despite
the huge stakes involved.
Companies whose profitability depends on knowing where
individuals go and when - billboard advertisers, transporters,
housing developers - have also been unable to crack the inner codes
of human movement.
Part of the problem has been the lack of reliable data. One
study of human mobility traced the distribution of half-a-million
bank notes through a population, using the bills as a proxy for
movement.
But notes change hands from owner to owner, breaking the thread
of an individual's migration.
A team lead by Albert-Laszlo Barabasi, a professor at
Northeastern, figured out a clever way around this shortcoming.
Randomly selecting 100,000 anonymous cell phone users from a
pool of six million, the researchers tracked individual movement
through calls made and received by recording the location of the
nearest relay tower.
Despite a total of more than 16 million 'hops' from one spot to
the next, 'the resulting statistics show a strikingly small
scatter' and thus add weight to the mathematical laws they
disclose, commented Nature in an editorial.
Even without knowing why people go where they go, the patterns
uncovered could, for example, provide crucial data on how to curb
the spread of a communicable disease.
Up to now, epidemic models lacked detailed data on human
mobility and had to rely on assumptions about random motion or
computer simulations, said Mr Hidalgo.
'Our results show that there are indeed some simple rules that
can be used to describe human mobility,' he said, adding that the
same type of problems apply to urban planning and traffic
forecasting.
'Epidemiologists will no longer be forced to work with highly
oversimplified models of infection rates and disease spread,'
commented Nature. -- AFP