There was a piece over at The Atlantic Cities that brings up an interesting topic, that of "Commuter-adjusted populations". This refers to cities whose populations grow during the workday when people who live outside a city commute in to work inside the city. As an example in the story, they state that the population of Manhattan which is normally about 1.5 million people undergoes a significant transformation during the workday when its population increases drastically.
This latter number – 3,083,102, to be precise, according to American Community Survey data collected between 2006 and 2010 – is in some ways an even more important one than the population figure we typically affix to places. If Manhattan ever needs to evacuate by day during a disaster, the city has to figure out what to do with all 3 million of those people. The city's transportation planners are responsible for every one of them, whether they live in New York or not.
This week I have been working on looking at historical crime data at the agency where I work. I managed to compile 40 years of UCR Part 1 crime numbers for the sleepy little burg where I work. In order to put those numbers into context, I also dug up 40 years worth of population estimates in order to calculate accurate crime rates and put those Part 1 crime numbers into proper context. There's a big difference between a population of 35,000 and one of 134,000.
If you work in a city with a significant "commuter-adjusted population" it's probably worth keeping these major population fluctuations in mind when you are looking at your crime rates.
Does your agency see major cyclical population changes? If so, how do you take this into account when calculating crime rates or allocating police resources?