By: Our Correspondent

Baidu, the enormously popular Chinese-language version of Google, launched a “heat map” before the Lunar New Year to show trends of where Chinese travelers were heading to and coming from as hundreds of millions headed for their homes for the traditional holiday, which began Jan. 31.

But Baidu and the police didn’t expect that it would show a massive and hurried migration out of the Pearl River delta city of Dongguan Sunday afternoon, when vast numbers of people fled for all points – as the police cracked down on the city’s notorious red light district.

It is estimated that 10 percent of the floating population of the sprawling factory city of 7 million people are engaged in the world’s oldest profession. By one estimate anywhere from 500,000 to 800,000 people are in some way employed in the sex trade. A staggering 300,000 sex workers, known locally as “technicians” according to the South China Morning Post, are thought to ply their trade in thousands of side-street massage parlors, exclusive hotels, spas and neon-lit karaoke bars.

Apparently that finally got too much for the Chinese authorities. In two news broadcasts, the state-owned CCTV television network charged that police had ignored prostitution in the city and allowed the industry to thrive for five years since the last crackdown. After viewing the CCTV reports, Guangdong’s party secretary Hu Chunhua ordered the raids.

The crackdown netted two suspended police chiefs, the shuttering of 12 “entertainment venues” and the arrests of scores and presumably left thousands of Hong Kong housewives questioning where their husbands had been on Sunday.

That prompted an exodus from the city in all directions – although, according to Baidu’s heat map, a full quarter of the departures headed for Hong Kong in a hurry. According to the Tech in Asia website, Baidu gathers data from smartphones with Baidu Maps and other apps using its location-based platform to create the heat map. Baidu Maps alone has more than 200 million registered users and receives 3.5 million position requests every day, according to Tech in Asia. The heat map updates every four to eight hours, showing the most popular destinations, points of origin, and travel routes.

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According to the map, in a report made public in the Hong Kong-based Marketing.trade publication, other cities that were destinations for the fleeing tourists were Ganzhou, Jiangxi, Guangxi Yulin, Chenzhou, Hunan and Zhejiang Ningbo. The Baidu live map visualizes the hottest migration routes. From 12 noon to 8 pm, the rush was on.