We look at New York City (NYC) and New York State to see what the connection is between population density and susceptibility to infection by Covid-19. Lots of people living very close to each other would intuitively seem to explain why NYC has such a large number of cases of a communicable disease.
Link to this post for sharing:
https://meetingthetwain.blogspot.com/2020/04/corona-virus-and-density-in-nyc.html
There is a definite and strong connection between Covid-19 and the NYC Metro area but it does not appear related to population density since some of the suburban counties with high infection rates actually appear to be rural. The main carriers of infection seem to have come from Europe to the North-Eastern US.
https://theintercept.com/2020/04/12/u-s-got-more-confirmed-index-cases-of-coronavirus-from-europe-than-from-china/
Other metropolitan areas in NY State have markedly lower infection and death rates than any of the urban or suburban counties around NYC. Whatever the reason, population density does not appear to be the cause.
Discussion:
Below is a map of Covid-19 cases in NYC by zip code - darker color = more cases. You don't need to be an expert on NYC geography to know that lower Manhattan is one of the densest parts of the city (and the world) yet it has relatively few cases of Covid-19.
For those unfamiliar with NYC, the following map of the 5 boroughs will be helpful:
When we look at a 3-D density map of NYC we see that Manhattan is very densely populated as is the Bronx, (the borough to the north-east of Manhattan). Yet Manhattan had a very low infection rate while the Bronx had a very high incidence of covid-19 infections. (click on image to enlarge).
Numerically we see that the highest number of cases per person was actually in Staten Island (8,112 persons/sq. mile), the least densely populated borough of NYC. The lowest number of cases per person was in the most densely populated borough - Manhattan (72,033 persons/sq. mile).
Since density doesn't match with Covid-19 infection rates, let us try matching the Covid-19 map with other maps of NYC to see if we can find some correlation. There are number of interesting "heat maps" based on various criteria in a Huffington Post article. The best match is a rent "heat map" of NYC seen below:
To show how they match we put the two maps side-by-side below with arrows showing some visual correlations of low infection rates with higher rent areas:
This seems to be a clear correlation. The higher the rent, the lower the infection rate. Why would that be?
The education level map from the same Huff-Post article shows similar correlations but not as strong - see below (click on map to enlarge):
In general, the higher the educational level, the higher the income so, based on the previous observations, you might expect higher educational levels to correspond to lower infection rates. But, there is a lot of variation within each profession so the correlation of (education vs. income) is not as high as that of (rent vs. income). See graph below:
So why would paying higher rent mean you are less likely to get infected by Covid-19?
A good guess is that people who work in jobs such as retail clerk, or fast food worker are more likely to live in lower rent housing. Their jobs put them in more frequent contact with more people and therefore they are more likely to be exposed to the virus.
On the other hand, a professional can work from home and interact with people over the internet with little chance of getting infected. There are undoubtedly professionals in low rent areas and fast food workers in high rent areas, but that is not as common as the reverse.
To make it more confusing, it turns out that data from a different source ( https://www.syracuse.com/coronavirus-ny/ ) shows several very suburban counties in the NYC metro area have higher rates of Covid-19 infection and deaths than Manhattan. See following table and map looking at positives and deaths per 10,000 persons (click on image to enlarge)
Orange County, NY has a population density of 471 persons/sq. mile, less than 0.7% that of Manhattan's, yet its "positives" rate is over 60% higher and the death rate is only 20% lower. Below is an aerial view of Warwick, the largest city in Orange County, NY.
It is notable that other counties in NY State have very much lower infection and death rates than any of these NYC or suburban counties. See table below, continued from previous table (click image to enlarge):
Why would NYC's suburban areas have higher infection and death rates than much of the city itself? It may be commuters to NYC catch the virus on a train to the city, or on subway once they reach NYC. Or perhaps the quiet, suburban neighborhood they live in lulls them into a false sense of security.
Those are guesses but there is clearly some connection with NYC. For example, the metro area of Albany-Schenectady-Troy has 1.1 million people but the counties in that metro area (listed above) have death rates less than 10% that of NYC and it's suburbs.
Might it be that because there are a number of international airports in NYC there are more travelers from abroad going there serving as carriers of the virus? The article below from"Live Science" indicates that as a factor.
https://www.livescience.com/why-covid19-coronavirus-deaths-high-new-york.html
Many more infected people arrived at NYC than at LA or SF, and one person living in New Rochelle (a city in the northern suburb of Westchester County) was a "superspreader" infecting many more people.
In any event, it is not population density per se that results in higher infections.
Why Does this Matter?
The reason I looked into this was because I know NYC well enough to know that it is not all skyscrapers. Staten Island would fit anyone's definition of suburban single-family-home neighborhoods even though it is just as much a part of NYC as Wall St. and Park Ave.
I was looking to see what the correlation is between density and infection rates. To my surprise, there isn't any. At least not an obvious one.
So who cares?
There is currently a rather fractious debate going on about the virtues of population density in urban areas vs. the less dense suburban areas. Those living in suburban areas have been getting a little tired of being called names and have seized on the Covid-19 infection rates of NYC as a point against density. However, the idea that density per se is conducive to the spread of viral infections does not appear to be borne out by the data.
Those arguing for or against density on the basis of infection rates will need to look elsewhere.
For this look at data, we have reached...
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| NYC is crowded. Seems like diseases should spread more easily. Do they? |
This intuitive idea fails. There is no obvious correlation between population density and known infection or recorded death rates. There does seem to be a correlation between "high rent" vs. "low rent" neighborhoods.
This seems to be true in the UK as well.
“People living in more deprived areas have experienced COVID-19 mortality rates more than double those living in less deprived areas. General mortality rates are normally higher in more deprived areas, but so far COVID-19 appears to be taking them higher still.”
Nick Stripe, Head of Health Analysis, Office for National Statistics. From:
For some unknown reason Covid-19 infection and death rates of some NYC suburban counties turn out to be higher than some NYC boroughs, including Manhattan. One might hypothesize that suburban commuters could contract it riding on trains into NYC, but then why would that produce a higher rate of infection than those who ride subways. I leave that as a possibility, but it needs an explanation as to why that would produce a higher rate of infection than that of those who already live in the dense environment and ride subways.
There is a definite and strong connection between Covid-19 and the NYC Metro area but it does not appear related to population density since some of the suburban counties with high infection rates actually appear to be rural. The main carriers of infection seem to have come from Europe to the North-Eastern US.
https://theintercept.com/2020/04/12/u-s-got-more-confirmed-index-cases-of-coronavirus-from-europe-than-from-china/
Other metropolitan areas in NY State have markedly lower infection and death rates than any of the urban or suburban counties around NYC. Whatever the reason, population density does not appear to be the cause.
Discussion:
Below is a map of Covid-19 cases in NYC by zip code - darker color = more cases. You don't need to be an expert on NYC geography to know that lower Manhattan is one of the densest parts of the city (and the world) yet it has relatively few cases of Covid-19.
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| Lighter areas have fewer infections. Darker areas, more infections. Data as of April 16, 2020. Map from https://www1.nyc.gov/site/doh/covid/covid-19-data.page under title "Percent of Patients Testing Positive by ZIP Code in NYC" (bottom of the page) |
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| From: https://en.wikipedia.org/wiki/Boroughs_of_New_York_City |
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| From: http://www.undertheraedar.com/2012/01/population-density-in-new-york-city.html |
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| https://www1.nyc.gov/site/doh/covid/covid-19-data.page |
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| The darker the color, the higher the rent. From Huffington Post: https://www.huffpost.com/entry/new-york-city-charts_n_6912310 |
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| Left map is Covid-19 infection rates. Right map is rent map. Arrows show 4 of the areas where low infection rates correspond to high rent areas. In general, lighter areas on left (fewer cases) correspond with darker areas on right (higher rent). |
The education level map from the same Huff-Post article shows similar correlations but not as strong - see below (click on map to enlarge):
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| "Degree" map of NYC. Highest educational levels are darkest orange, lowest are darkest blue. Some similarities with infection rate, but not as significant as rent map. From: https://www.huffpost.com/entry/new-york-city-charts_n_6912310 |
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| The average Economics Major makes more than the median Humanities major, but the top 10% of Humanities majors make more than the average Economics major. Chart from: https://www.ngpf.org/blog/question-of-the-day/question-of-the-day-what-college-major-provides-graduates-with-the-highest-median-career-earnings/ |
A good guess is that people who work in jobs such as retail clerk, or fast food worker are more likely to live in lower rent housing. Their jobs put them in more frequent contact with more people and therefore they are more likely to be exposed to the virus.
On the other hand, a professional can work from home and interact with people over the internet with little chance of getting infected. There are undoubtedly professionals in low rent areas and fast food workers in high rent areas, but that is not as common as the reverse.
To make it more confusing, it turns out that data from a different source ( https://www.syracuse.com/coronavirus-ny/ ) shows several very suburban counties in the NYC metro area have higher rates of Covid-19 infection and deaths than Manhattan. See following table and map looking at positives and deaths per 10,000 persons (click on image to enlarge)
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| The 5 suburban counties of Nassau, Suffolk, Westchester, Rockland, and Orange all have higher infection rates (boxed in green) than most of the boroughs of NYC. Three have higher death rates (boxed in blue) than Manhattan. |
The suburban counties mentioned above are shown below for those unfamiliar with the area.
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| Map of NYC and it's suburban counties. Orange and Rockland Counties are more rural than suburban. |
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| Warwick, NY - largest city in Orange County, NY Google Maps satellite view |
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| Counties in other parts of NY State have far, far lower rates of "positives" or deaths per 10,000 persons than NYC and its suburbs |
Those are guesses but there is clearly some connection with NYC. For example, the metro area of Albany-Schenectady-Troy has 1.1 million people but the counties in that metro area (listed above) have death rates less than 10% that of NYC and it's suburbs.
Might it be that because there are a number of international airports in NYC there are more travelers from abroad going there serving as carriers of the virus? The article below from"Live Science" indicates that as a factor.
https://www.livescience.com/why-covid19-coronavirus-deaths-high-new-york.html
Many more infected people arrived at NYC than at LA or SF, and one person living in New Rochelle (a city in the northern suburb of Westchester County) was a "superspreader" infecting many more people.
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| New Rochelle, Westchester County, NY |
Why Does this Matter?
The reason I looked into this was because I know NYC well enough to know that it is not all skyscrapers. Staten Island would fit anyone's definition of suburban single-family-home neighborhoods even though it is just as much a part of NYC as Wall St. and Park Ave.
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| 271 Isablella St., Staten Island - New York City |
So who cares?
There is currently a rather fractious debate going on about the virtues of population density in urban areas vs. the less dense suburban areas. Those living in suburban areas have been getting a little tired of being called names and have seized on the Covid-19 infection rates of NYC as a point against density. However, the idea that density per se is conducive to the spread of viral infections does not appear to be borne out by the data.
Those arguing for or against density on the basis of infection rates will need to look elsewhere.
For this look at data, we have reached...
