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" After a disaster, people scatter. Earthquakes, hurricanes, or even droughts are surefire ways to clear out a city. But no matter where displaced people move, their exodus creates a serious issue for aid workers: You can&amp;#039;t help anybody unless you know where they are.  &amp;quot;It&amp;#039;s almost impossible to study these things,&amp;quot; says Linus Bengtsson, of the department of public health sciences at Sweden&amp;#039;s Karolinska Institute. &amp;quot;Having people count other people on the sides of the streets is extremely difficult.&amp;quot; But thanks to new research out this week in the Proceedings of the National Academy of Sciences by a team including Bengtsson, figuring out where people go after a natural disaster might get a little bit easier.  Most of the post-disaster people-tracking data that researchers have collected over the years comes from indirect means like school enrollment records and tax forms. While those methods work well when looking back on a disaster, they don&amp;#039;t provide any information that could help relief workers find people in need of help in the immediate aftermath.  To get a more real-time look, Bengtsson and his colleagues convinced Digicel\u2014the biggest cellphone-service provider in Haiti\u2014to supply them with GPS data for every cell sold before the 2010 Haiti earthquake in hard-hit Port-au-Prince. (Admittedly, this brings up some Big Brother concerns. But the researchers and the company assure us that the people behind the cell data remained anonymous. Digicel provided one locating piece of information per phone per day, and the scientists never knew who the people using the cells were.) By tracking the location of one &amp;quot;chargeable event&amp;quot;\u2014anything your phone does that requires a satellite, including calling, texting, and emailing\u2014the researchers saw where the phone and its owner had moved over 24 hours. The scientists got a large sample of Haitians this way: About 50 percent of the adults in Haiti have cellphones, and Digicel services most of them. All told, the study used cell data from 42 days before the quake to 341 days after it to track 800,000 cell owners in Port-au-Prince the day of the disaster. The researchers found that after the initial shock of the earthquake passed, people resumed normal movements surprisingly quickly. The Haitians who left Port-au-Prince needed to travel farther distances to find work, food, and shelter, but after they settled somewhere new they fell into a routine almost immediately. &amp;quot;Even though they moved across longer distances and across bigger areas,&amp;quot; Bengtsson says, &amp;quot;the regularity [of their movements] didn&amp;#039;t change. After the first three months, they got new regular habits. It changed their behavior but not the regularity of it.&amp;quot; While it&amp;#039;s nice for relief workers to know that in the immediate aftermath of a disaster people will return to a normal schedule in Haiti, it doesn&amp;#039;t mean that this will hold true for every disaster in every country. &amp;quot;My concern is overgeneralizing,&amp;quot; Nathan Eagle, a professor at MIT unaffiliated with the PNAS paper, says. &amp;quot;We have a data set of one. This is one example, and it&amp;#039;s great. There&amp;#039;s something to be said about how people behave in a disaster, but you don&amp;#039;t want to overgeneralize it to every disaster.&amp;quot; However, this paper did allow researchers to see exactly where people decided to flee. Because the quake occurred just after New Year&amp;#039;s Day, the researchers got GPS data showing where Haitians went to spend the holidays. It just so happens that many of the tracked individuals went back to those same places after the quake. &amp;quot;These results are probably transferable to other disaster contexts,&amp;quot; Bengtsson says. &amp;quot;People go where there is close social support.&amp;quot; Bengtsson and Eagle both think cellphone data could be key to keeping track of people affected by natural disasters. If aid workers know where populations are likely to end up when displaced ahead of time, then they will be able to get the right kind of relief to the right areas. Cellphones have become so omnipresent in nearly every part of the world that this tracking could be done after just about any disaster. &amp;quot;This [cellphone] data is a fact of life,&amp;quot; Eagle says. &amp;quot;It&amp;#039;s a necessary byproduct of the ubiquity of cellphones. Given the fact that it does exist, we should find ways to use it to benefit the lives of people who are generating it.&amp;quot; "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/science/environment/a11949/cellphone-signals-can-find-people-scattered-by-disaster-9842813/>