Satellite data previously used by NASA to map the Earth’s land masses has been combined with census data from 1990 to 2010 in order to map the planet’s people instead, or at least those in the United States. The new map, produced by the University of Cincinnati, offers unprecedented insights into the kaleidoscopic spread of diversity in US neighbourhoods.
Maps have been created using census data before, but usually in much less detail. This is because the census contains sensitive information such as participants’ income and education, so the government instead takes averages in large blocks measuring three square kilometres in urban areas and 108 square kilometres in rural regions. ‘Privacy is assured but it costs a significant – in some cases very significant – loss of spatial accuracy,’ explains Anna Dmowska, postdoctoral researcher and co-author of the maps. For example, if the block area is large but only a small portion of it is lived in – perhaps due to lakes, factories or parks – the block data would inaccurately show it as all being inhabited.
The problem facing Dmowska and her team was finding a way to get better results without better data being published. ‘We created a more detailed distribution of population using the NASA-derived National Land Cover Database – which is available at a 30-metre resolution,’ she says. In other words, they made the land clearer, taking populations out of the uninhabited places. The result allows a deeper look at racial diversity, without compromising privacy.
By flipping through the 1990, 2000 and 2010 overlays, it is possible to see the wax and wane of cultures in the US with orange showing Non-Hispanic white communities, green showing Non-Hispanic black communities, red showing Asian communities and blues showing Native American (and other minority) communities.
Zoomed out, the countryside shows mostly white populations at low densities, with pockets of Native Americans communities on reservation land and the ‘curve’ of African American populations from the east coast to the Mississippi river. At city level, where populations are denser, the results stand out. It is possible to see how the cultural fabric of San Francisco has changed between 1990 and 2010, when the Silicon Valley and technology boom created an influx of Asian households.
A cultural change can also be seen in the northern city of Chicago, which has one of the largest US populations of Mexican-born immigrants, second only to Los Angeles. Though a long way from the Mexican border, Chicago has long been dubbed a ‘gateway city’ as it is easily accessed by rail and during the 1990s, Mexican immigrants made up an enormous 105 per cent of the city’s population growth, which can be seen blossoming in the downtown centre. By the 2000s, however, Mexican immigration began to drop as the recession made Chicago (and the US as a whole) less of a draw for Mexican immigrants. Those who did migrate began to choose less expensive towns and suburbs instead. In 2015, the city reported its first population loss in almost a decade – 11,327 residents. A drop which, in 2016, then jumped to 19,750. The push factors have been put to inner city gentrification and tighter control of legal and illegal immigration under President Trump.
The maps also show the difference between diversity and integration. ‘People don’t realise that the United States is a diverse country but at the same time is still very segregated,’ said Tomas Stepinski, geography professor at the University of Cincinnati and a co-author of the maps. Often the two factors come together. Chicago, again, is a case point. At city-level it is one of the most diverse in the country but at a neighbourhood level, the populations are among the most segregated. Its division was born from racist housing contracts that prevented white families from selling homes to African-American families. These were removed in 1948 but ‘white flight’ and social inequality meant that community separation remained. Other diverse but segregated cities are Detroit, St Louis, Baltimore and Washington D.C.
They can be compared with the cities of Sacramento in California and Jersey City in New Jersey. Within them, ‘the grey colour indicates those rare places where diversity is “high”,’ says Dmowska. ‘That means more than two races are present and no race is dominant over remaining races.’
Dmowska was taken aback by some patterns in the map. ‘The most surprising finding is the realisation that white-only neighbourhoods are in retreat everywhere in the US,’ she says. ‘Neighbourhoods become more diverse.’ There are two other patterns to notice, she says: ‘Old African-American-only neighbourhoods are persisting albeit they don’t expand. At the same time, new low-diversity neighbourhoods are forming – these are dominated by Hispanic and Asian populations.’ The 2010 census showed that Asians surpassed Hispanics as the fastest-growing racial demographic in the US, mainly due to higher birth rates and migration levels.
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