We know how much you all love a demographics-based animation. So today, because it's Thursday and we're feeling kind, we've found you another one. This time, it's a 3D representation of Manhattan's population density fluctuations between 1810 and 2010, created by business school NYU Stern's urbanisation project.
First, some background. Manhattan, as you'd expect, grew gradually more populous from 1800 onwards, starting at the penninsula's southern tip. By 1916, it looked like this:
Those intimidating-looking blocks of people on the lower and upper east sides were mainly made up of immigrants, many of whom lived in cramped tenement blocks. At first glance, you might assume the city's core borough would only have become denser in the past century. Actually, though, what happens next is this:
Those heavily populated sections appear to be shrinking.
But of course, the animation misses off the city's other boroughs, which where much of that density was absorbed. Throughout the 20th century, the population of New York City as a whole has grown steadily (bar a small dip in the 80s), from 3.5m to around 8m by the millenium. Manhattan's population, meanwhile, has fallen over the past hundred years.
Here's the animation in full:
As you can see, density rises and falls across Manhattan throughout the 200 years – but by 2010 the levels have settled to a roughly consistent spread across the land mass.
London is another city which bucks the worldwide trend for massive density spikes at its centre. In that respect, indeed, it's done much better than New York City :
Current population densities in London (L), and New York City (R). Images: LSE Cities.
While a high city density can bring benefits in terms of better use of public money and more widespread use of public transport, it is possible to become too dense. Packed residential areas like New York's tenement blocks, or slum areas in South American cities, can bring with them disease, informal and unsafe buildings, and rising inequality.
As we've seen in London and New York, good, cheap transport links to the greater metropolitan area, plus healthy, connected suburbs, can help cities escpape these pitfalls.