Re: currency spend analysis vs. disease

A review of "The scaling laws of human travel", a 26 January 2006 Nature
magazine article by D. Brockmann, L. Hufnagel & T. Geisel.
---

The vast majority of the letter is complex statistical & graphical
validation of their theoretical model validly describing dispersal of bank
notes and human travel behaviour. The core data the analysis was based on
consists of 1,033,095 reports on the locations of 464,670 dollar bills
reported to whereisgeorge.com.

"Only 23.6% of the bank notes travelled farther than 800 km, whereas 57.3%
travelled an intermediate distance greater than 50 but less than 800 km,
and a relatively large fraction of 19.1% remained within a radius of 50
km, even after an average time of nearly one year."

The conclusion reached is that human travel can be described by a
continuous-time random-walk process that incorporates scale-free jumps as
well as long waiting times between displacements and on geographical
scales is an ambivalent and effectively superdiffusive process. In simpler
language, that means humanity is in constant movement. We are constantly
going everywhere & back again without apparent rhyme or reason and are as
likely to go down the road, on a several-hour long trip or even to the
other side of nation (remember, the analysis was conducted on those in the
US). However, staying in one place for long stretches of time is just as
likely. This model has long been regarded as a maxim, a saying widely
accepted on its own merits, but to their knowledge, this is the first
empirical evidence of this phenomenon.

"We believe that these results can serve as a starting point for the
development of a new class of models for the spread of human infectious
diseases, because universal features of human travel can now be accounted
for in a quantitative way."


The text in full can be found, courtesy of University of California, Santa
Barbara, at [ http://www.kitp.ucsb.edu/community/news/Hufnagel_Paper.pdf
].


Viking Coder
____________
http://420000.e-gold.com