The question of how many police officers New Orleans should have has been debated since long before Hurricane Katrina. In researching this article, I came across discussions from the late 1990s of NOPD’s recruiting goals, and how large city leadership thought the force should be.

Among the problems with looking at this question are that 1) there is no correct answer, only educated analyses; and 2) there is no easy way to measure if we’ve reached the “right number.”

That having been said, data do exist that can help guide the discussion of how many police officers New Orleans should ultimately aim for and what the expected results of expanding NOPD should be.

How Big Should NOPD Be?

NOPD finished 2015 with 1,163 sworn officers, a number that most people seem to agree is too small. The force lost 22 percent of its officers between late 2008 and the end of 2014, the fourth-biggest drop for any police force in the country over that span.

I would propose that any discussion of how big NOPD should be should not begin with a raw number, but with a ratio of officers relative to the city’s population. This can be fairly easily calculated using the FBI’s Crime in the United States series for every year since 1995. New Orleans did not provide a number of officers for 2009, so I estimated its value between 2008 and 2010’s totals, and the 2006 figures were a little wonky, so I removed them for the sake of clarity.

A ratio of 330 to 350 officers per 100,000 residents closely matches up with the median ratio for the country’s most violent cities. The 20 cities with the highest violent crime rate in 2014 (per FBI data) had a median ratio of 315 sworn officers per 100,000 residents.

Given all of this information, I would set the goal for the number of NOPD officers at 330 per 100,000 residents. This number would be near where we were from 1998 to 2005, while reflecting roughly what most cities like New Orleans have.

Determining how many officers to hire by 2020, therefore, should be based on reasonable projections of New Orleans’ population might be in that year. Quick disclaimers: I am not a demographer and do not profess to have real insight into how big New Orleans will be in 2020. There are also numerous eventualities — from a national economic recession to a natural disaster to a Saints Super Bowl parade discovering oil under the Dome — that could influence how big the city will be in five years.

That said, we can use 2007-2014 population data from the FBI and the U.S. Census to at least ballpark where New Orleans will be in 2020, and apply that figure to a proposed NOPD manpower count. Both the FBI and the Census Bureau put New Orleans’ population at 220,000 to 240,000 in 2007, and around 385,000 in 2014.

To estimate the city’s 2020 population total I simply plugged the city’s population for 2007 through 2014 and created a logarithmic trendline in Microsoft Excel. I then used that trendline to extrapolate where we’ll be in each of the next five years. The results (shown below in red) suggest New Orleans will have between 423,000 (Census data estimate) and 433,000 (FBI data estimate) residents in 2020.

Adding Police Will Likely Reduce Crime in New Orleans

The second part of the equation is analyzing what adding officers would do for New Orleans. Looking at crime and NOPD size from 1995-2014 suggests that crime will likely go down as the department grows. This assessment is even stronger when comparing national crime and police department growth trends.

The easiest way to prove this idea is to look at how many NOPD officers were added or lost each year between 1995 and 2014 and then comparing that to the change in the number of violent crimes per 100,000. The correlation is extremely high (r = -.82), meaning that as officers went down during this period violent crime went up, and vice-versa.

Another way of looking at the problem is to compare police growth and changes in crime for cities throughout the country. There were 70 cities with populations of at least 250,000 people that produced population, crime and police sizes for 2010 – 2014.

Overall there was a negative correlation (r = -.36) between the percentage change in a police department’s size and the percentage change in its violent crime rate in the five years between 2010 and 2014. In other words, if a police department shrunk from 2010 to 2014, then the city likely experienced more crime in 2014 than in 2010. The correlation is even stronger (r = -.49) among the 22 cities like New Orleans that had between 1,000 and 2,000 police officers in 2010.

In other words, adding more police officers appears to produce positive results for crime reduction, and vice-versa. Obviously there is a lot that goes into successful crime reduction, and policing is just one component. The data suggest, though, that growing NOPD would help reverse the trend of rising crime since 2010 and put us back on the pre-Katrina crime reduction path.