Safest, & most perilous cities

What do the Massachusetts’ cities of Franklin, and Fall River, have in common?  Or the Illinois’ cities of Lake in the Hills, and East Saint Louis?  In both states, we highlight one of the safest 100 cities in America, and we also highlight one of the 100 most dangerous cities in America.  There is a somewhat positive relationship between there being a state’s safety inequality, and states that boast cities that are EITHER the most dangerous or those that are the safest.  Turns out that generally states are either having all of their cities that are or mediocre safety, or (as seen below for the generally most-populated) states where the safest cities exist and where in the same state there are some of the most perilous cities as well.  This is a biased result based on subject criteria including the recognized perception of the city.

Let’s firstly explore this raw ranking of states below.  Massachusetts is shown first and hosts 21 of the nation’s top 100 cities, and 6 of the nation’s 100 most unsafe cities, according to a realty data analytics firm.  Next, we see Illinois, with 7 and 6 cities hosted respectively.  By the time we get to New Jersey (the 6^th state shown on chart), we will account for the top 6 states (generally the most populated as well) hosting a total of 61 of the 100 safest cities, and 38 of the 100 most dangerous cities.  Clearly some of these states are generally biased as the safest, though most are simply a checkboard of issues.  New Jersey only has 2 of the top 100 safest cities, which in no way offsets them having a record 10 of the 100 most dangerous cities.

All in all though, we see both lists accumulate somewhat in parallel, for the first 30 or so states.  In a couple handful of (generally less populated) states that are not shown at all, those states hosted neither a safest nor most perilous city.  If we independently cumulative-sorted each curve (most safe, and the most dangerous), the rankings shown should nearly 90% match what is shown here! 

Now of course, there is not always a perfect pattern in term of the number of cities a state has to begin with.  The District of Columbia is on of the 100 most dangerous cities, yet is only one city so doesn’t have a chance to have an offsetting top 100 safest city hosted as well.  One way to measure safety polarization in these tails is to look at the number of safest and most dangerous cities that are hosted, in relation to the number of cities to begin with in that state.  While New York and Texas are roughly the same population and number of cities magnitude, the latter state has a multiple of the number of top 100 ranked cities versus the former.

We see referring back to the topmost chart as well that Massachusetts has high safety imbalance, with >2/3 of their cities either among the safest in the country or the most perilous in the country.  Are they really 25x more extreme in safety versus other states?  No.  On the other hand, while Pennsylvania perplexingly has the greatest equality in the sense for such as large state with so many cities peppered throughout: they only had a couple cities among the top 100 most safe, and the same number of the top 100 most dangerous (a total of <5% which is exceptionally low for the U.S.)  This bias in big data analysis is probabilistically identical to the one reached previously where most-populated states have greater wealth inequality relative to one another (here, here, here).