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Traffic deaths, safety and suburbia, Part 2

A couple of months ago, I wrote a blog post comparing the safety of inner suburbs and outer suburbs. (See )

My post showed that (in least in the metropolitan areas I looked at) inner suburbs were safer than outer suburbs, because violent deaths from murder and traffic combined were lower in the former.

Michael Lewyn | July 15, 2012, 11am PDT
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A couple of months ago, I wrote a blog post comparing the safety of inner suburbs and outer suburbs. (See )

My post showed that (in least in the metropolitan areas I looked at) inner suburbs were safer than outer suburbs, because violent deaths from murder and traffic combined were lower in the former.

However, I devoted only a couple of lines to core cities (and, as some of the comments suggested, perhaps a few lines too many).(1)  It seems to me that comparing core cities to suburbs is not quite ideal, because typically, a regional central city contains a wide variety of neighborhoods- some very safe, some not so safe.   In an ideal world, one would resolve this problem by comparing individual neighborhoods or groups of neighborhoods to suburbs.  But this technique is not feasible because neighborhood crime statistics are not easily available for most cities (let alone neighborhood traffic fatality statistics). 

An alternative way to compare cities to suburbs is to look at "intown suburbs"- places that, although technically suburbs, are so close to downtown as to effectively be city neighborhoods. For example, in Atlanta, the city limits extend about 10 miles out from downtown in some directions, so Decatur (6 miles out) is an intown suburb.  If a region's intown suburbs have a lower "traffic + homicide" death rate than its outer suburbs, one can plausibly argue that  (parts of) cities truly are safer than outer suburbs.

I began my research with the following educated guess: low-income intown suburbs are more dangerous than wealthy outer suburbs, high-income intown suburbs less so.  Does data bear this out?

I chose Boston as a case study because Boston is one of the few cities with a mix of low-income and high-income intown suburbs.  So I focused on Chelsea (low) and Cambridge (higher).  Between 2005 and 2009, Chelsea had 4.6 murders per year per 100,000 people, and 4.9 traffic deaths, for a total violent death rate of 9.5 per 100,000.  More affluent Cambridge had 1.8 homicides per year and 2.1 traffic deaths, for a total violent death rate of 4 per 100,000.  An even richer (though more suburban) intown suburb is Brookline, which begins about four and a half miles from downtown Boston.  Between 2005 and 2009, Brookline had 0.4 murders per 100,000 per year, and 1.1 traffic fatalities, for a total violent death rate of 1.5 per 100,000 per year. Thus, the low-income intown suburb (Chelsea) was apparently more dangerous than the high-income ones (Cambridge/Brookline).  But how do both compare to real suburbs?

Since William Lucy's research (which led to my work)(2) focuses on the relative desirability of city and suburb, I chose one of the most desirable suburbs as a case study of an outer suburb: Newton (an inner ring suburb about 6 miles from Boston) and Sudbury (18 miles out, the region's fifth wealthiest suburb)(3).  Sudbury had 4.5 traffic deaths per year per 100,000 and 1.2 murders, for an overall violent death rate of 5.7- 40 percent more than Cambridge, and far more than Brookline. Sudbury's figures are fairly typical; in 2005-06 Middlesex County (which includes Sudbury and numerous other, mostly outer-ring, suburbs) had about the same level of traffic deaths.  (No countywide data were available for 2007-09).

 My discussion so far hasn't taken account of the distinction between homicides caused by strangers (and thus arguably more threatening to the public as a whole) and those caused by acquaintances.  Unfortunately, digging up statistics on this issue is difficult- not just because individual municipalities' statistics may not be easy to obtain, but because many homicides are unsolved (which means we don't know whether they were "stranger homicides").  However, nationally we know that about 12 percent of murders were committed by persons who the victim did not know, but that the murderer/victim relationship was unknown as to an additional 44 percent of homicides.(4) If you assume that only the 12 percent figure matters, the gap between Chelsea and Sudbury narrows quite a bit: Chelsea's violent death rate plummets to 5.5, only about 20 percent higher than Sudbury's.  But if you assume that 56 percent of murders involved strangers, then Chelsea's "stranger violent death rate" is 7.5, still about 50 percent higher than Sudbury's.

 Another city with both high- and low-income intown suburbs is Detroit.  Grosse Pointe, less than 6 miles from downtown Detroit, had zero traffic deaths between 2005-09, and only 3.6 homicides per 100,000 per year, for an overall "violent death rate" of 3.6.  By contrast, working-class Hamtramck, surrounded by the city of Detroit, had 7.5 murders per 100,000 and 2.9 traffic fatalities for a total violent death rate of 10.4.    

How does these results compare to those of "nice" outer-ring suburbs? One of the wealthiest suburbs in America, Bloomfield Hills, had no murders and 5.2 traffic deaths per 100,000- slightly worse than Grosse Pointe, but perhaps not significantly so since only one death was involved, artificially knocking up the rate for a very small suburb.  On the other hand, nearby Birmingham had only 2 traffic deaths per 100,000, even lower than Grosse Pointe.    Oakland County as a whole had 6.3 traffic deaths per 100,000 people in 2005-06; however, the county includes inner-ring as well as outer-ring, and middle-class as well as upper-class, suburbs.

 So my examples (admittedly the tip of a very large iceberg) back up the theory that lower-income urban places are less safe than suburbs.  They also suggest that well-off intown suburbs like Brookline and Grosse Pointe are as safe or safer than outer suburbs.  However, the data is unclear as to which adjective ("as safe" or "safer") applies.  

Having said that, I wouldn't pretend any of this is any more than a starting point for discussion.  A more comprehensive article would create a much larger database of (1) intown suburbs, (2) inner suburbs and (3) outer suburbs, and would discuss a broader demographic range of suburbs.




(1)One of the comments pointed out that I did not distinguish between homicides caused by strangers and those caused by acquaintances – for more on this, see my last paragraph on Boston suburbs.

(2) .  Lucy's data is mostly by county; but county-by-county data does not always distinguish inner from outer suburb, or outer suburb from rural area, because outside the largest metro areas a county can include a very wide range of places.  For example, Detroit's Oakland County borders Detroit, but contains a lot of suburbs that are quite far from the city.

(3)The four wealthiest (Weston, Dover, Carlisle and Sherborn) lacked crime and/or traffic data for all five years studied.  


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