*When I wrote this post, I was working with a map of China at the prefecture level (the next level below province). After writing, the author of the map， 风雪祁连 （框框), shared with me an even more detailed map, this time at county level (the next level below prefecture). I've added this new map to the bottom of this post

When I first saw this map, my heart went aflutter. The data it contains is simple enough, but so rich with significance. 

Each prefecture or prefecture-level city in China is colored according to its net migration rate. Those with net in-migration are red,  out-migration blue, the deeper the shade of red or blue the greater the rate. What emerges is a detailed overview of what China's highly variegated inter- and intra-regional migration patterns. 

Some things should come as no surprise. Beijing, Shanghai, and Guangzhou, as expected, are deep red magnets for migrants. Centers of the country's cultural, financial, and manufacturing industries and engines of economic growth, their ancillary construction, service, and manufacturing industries have been attracting low-wage migrant workers for decades. 

High costs in the major cities have pushed many firms, especially manufacturers, into neighboring and peripheral cities; places like Tianjin, Hangzhou, and Zhuhai are major job magnets in their own right. So entire megaregions—the Bohai Bay region around Beijing, the Yangtze Delta region around Shanghai, and the Pearl River Delta (PRD) region around Guangzhou—also appear deep red. 

Other regions along China's coastline are red too, but a lighter shade of red. These include the Liaodong Peninsula (anchored by Dalian), the Shandong Peninsula (with Yantai and Qingdao), and the Zhejiang-Fujian Coast (with major nodes in Wenzhou, Fuzhou, and Xiamen). As China's high speed rail network enters maturity, these coastal regions, once separated by days of travel but now just hours on bullet trains, will likely integrate even further into what will become an unbroken corridor of development along the entire eastern seaboard. 

Turning now to the blue areas, the origins of the migrant workers, the trend is in our face: central China is nearly completely blue. Of course, it's not black and white. Some regions of central China are bluer than others. They are places like Henan, Sichuan, and Guizhou, provinces with either historically poor populations, historically high populations, or both. 

Some clear exceptions to the central Chinese migratory drain effect stand out. They are the provincial capitals. In almost each predominantly blue central province, that province's capital sticks out as a lone island of red. This makes social and economic sense. Chinese political geography hews to the primate city principal. That is, unlike in the US where state governments are often located in smaller cities like Sacramento (California) and Springfield (Illinois), Chinese provincial capitals are without exception the largest cities in their respective provinces. Hence, they exert economic pull even in regions with net migration loss. For many young people leaving their home for the first time, the nearest provincial capital is often a stepping stone before going further afield to a Beijing or a Guangzhou.

Guangdong Province exhibits properties of both pull and push dynamics. The PRD region, as previously discussed, is a magnet for labor from the entire country. But what of the rest of Guangdong province? Here we see a sharp contrast between a deep red PRD, and the deep blue of the remainder of the province. Clearly, the PRD is attracting migrants from both far and near, including migrants from neighboring prefectures within the same province. These nearby migrants probably have the best of both worlds. Unlike migrants from far-away provinces, they don't have to worry about scrambling for train tickets home at the holidays. They can visit their families far more frequently. They also speak the same language (Cantonese), so they don't stand out so much as outsiders. The proximity of rural areas like northern Guangdong to high-paying jobs helps explain why visitor to visitors find villages full of modern houses. These rural economies have benefited the longest and the most from remittances. 

Let's now turn to another area of the map that needs explaining. Clearly, large swaths of western and northern China don't fit the pattern. We see large red prefectures in Inner Mongolia, Tibet, Qinghai, and parts of Xinjiang, the latter three of which are the poorest provinces in China. Why then the net in-migration? Well, to begin with, this region of China has the lowest population, and population density. Remember this map is showing net migration as a percentage of total population, not total number of migrants. Therefore, in some of these low-population prefectures, it takes a relatively small number of incoming migrants to produce a high migration rate. Also, there's the coarseness data. Prefectures in western China are as large in area as they are low in population. The actual destination of the incoming migration is probably highly concentrated—in cities, or areas with natural resources such as mines or oil fields. Were the data behind this map available at a finer-grained level of detail—say, county-level administrative units—then the west probably wouldn't be so uniformly red. The vast majority of Northern Tibet, which appears red on this map, is uninhabitable wasteland.

Inner Mongolia, a province to which I've never been, exhibits some very interesting patterns on this map which I wanted to investigate more closely. One of China's largest provinces, it stretches over 2,400 kilometers from west to east as it hugs the Mongolian border. The western part of the province appears deep red on this map, while the eastern part is light blue, and two prefectures in the middle deep blue. Upon read up on the prefectures of Inner Mongolia individually, the factors behind their varying migration rates become clear. There is a natural resources boom taking place in western Inner Mongolia. The region is rich with coal, but also with rare earth minerals; 45% of the world's supply is found within Inner Mongolia's Baotou prefecture alone. Also, the government is active in forcing Inner Mongolia's last remaining nomads to relocate to permanent settlements. Much of this population lives in the grasslands of Hulunbuir in the northeast. 

Finally I want to turn my attention to Yunnan Province, where I have lived for the last four years, and therefore with which I am most familiar. Yunnan is rather unique; it doesn't exactly fit into any of the migration trends I've described above. It's not a major nexus of urbanization and manufacturing like Shanghai or the PRD. But it's also not a huge migrant drain like most  inland provinces. Nor is it a unique migrant magnet like the natural resource-rich Inner Mongolia. 

So what exactly is happening in Yunnan? First, the three eastern prefectures—Zhaotong, Qujing, and Wenshan—are blue. It's not a coincidence that they neighbor Sichuan, Guizhou, and Guangxi provinces, which are very much in the migrant drain region. Densely-populated, Han-dominated Eastern Yunnan has always been more connected to what's happening in central China than the rest of Yunnan, which is more sparsely populated, and home to ethnic minorities with cultural and linguistic ties that stretch across Yunnan's international borders into Southeast Asia. 

Turning to the rest of Yunnan, we see nine prefectures with net in-migration, three with net migration roughly even, and only one with net out-migration. This is fascinating to me. I've called Yunnan my home for the last four years, I love it here, and I know that Yunnan people love it too. But this is the first time I've seen data like these which actually suggest that Yunnan people are so happy in their home province that they they're not leaving. When you look at Yunnan just based on national economic indicators alone, there ought to be more out-migration, because Yunnan is still relatively poor. 

But clearly there's something about Yunnan that keeps people here. I'm going to go out on a limb and guess that climate, and the lifestyle that goes along with it, is a major factor. Take two farmers at random and try to compare the overall quality of their lives. They may be similar if you analyze just economic indicators. But if one farmer lives in not-too-hot, not-too-cold Yunnan, and one lives in Heilongjiang, with its hot summers and freezing winters, then it's safe to say that the Yunnan farmer has a more comfortable life, one that he'd be less willing to sacrifice for a few extra RMB he could earn if he migrated.

What about the fact that Yunnan is actually attracting new residents? I'm guessing the tourism industry is one factor. Xishuangbanna, Diqing, and Lijiang are major tourism destinations, and a lot of people trying to get in on the tourism boom are not locals but outsiders. Dehong, Lincang, Yuxi, Honghe, and Yuxi have nascent tourism industries too, but not enough to explain the increased migration. Trade with neighboring countries could be a factor. Borders in these prefectures with Myanmar and Vietnam are being upgraded, new import-export zones established, and new and improved infrastructure is making trade more feasible. 

This map is just a beginning. First I need to get my hands on the data set behind this map. Then I'd like to then explore these trends in Yunnan at the county level rather than merely prefecture level. An even richer map would 

attempt to illustrate precisely where the actual migratory flows are occurring. Such a map would use arrows of varying thicknesses to give a more detailed picture of where migrants are coming from and going to. I've seen a very simple (and now outdated) version of this type of map before, in Cindy Fan's 2004 article "Gender Differences in Chinese Migration". 

1. This map is not my own, but the creation of a Chinese netizen by the name of 风雪祁连 (框框), whose personal website appears to be here. I found the map on this website. 

2. http://www.colorado.edu/geography/class_homepages/geog_3822_f09/CourseResources.htm

3. http://www.amazon.com/Changing-China-A-Geographic-Appraisal/dp/0813334748/ref=sr_1_1?ie=UTF8&qid=1378797721&sr=8-1&keywords=Changing+China%3A+A+Geographic+Appraisal