Do we have enough police in Australia to manage our security needs? This is an important question because we spend more than A$10 billion a year to pay for the police services that we have. Should we spend more?

Let’s start with a little history. We have more police per head of population than ever before. Australia had 129 police officers per 100,000 population a century ago. Twenty years ago the figure was 221 per 100,000. It is now 270. Of the states, South Australia tops the list with 314.

So there are more police. But if crime rates are rising, even these extra police numbers will be inadequate to meet the task of keeping us safe. True? No.

Fact: crime rates are falling

The fact of the matter is that crime rates are not rising. Over the last 15 years, generally speaking, crime has fallen – dramatically in some cases.

Figures show the following percentage changes in police-recorded crime across Australia from 2001 to 2011: fraud down 12%, arson down 14%, criminal damage down 22%, theft down more than 30% and burglaries and robberies down 50%. Even the numbers of homicides, which usually remain relatively stable, decreased by 23%. Car theft was down a staggering 60%, a trend that continues today.

The only crimes for which police recorded increases during that period were assaults (up 12%), shop theft (up 10%) and sexual assaults (up 3%). However, there is always a suspicion that these numbers often simply reflect levels of confidence in reporting by victims.

The above trends are mirrored by the data emerging from victimisation surveys. These are very useful in helping to eliminate the “dark” figure of crime that bedevils official police data.

The Australian Bureau of Statistics (ABS) keeps very good victimisation data. The ABS reported in 2015 that the number of recorded victims across Australia decreased for the majority of offence categories between 2013 and 2014.

Robbery had the largest proportional decrease of some 16%. Homicides and car theft are two of the most reliable indicators of the accuracy of victimisation figures, as they rarely suffer from reporting or counting problems. The numbers of homicide and motor vehicle theft victims fell to five-year lows, along with victims of abduction, robbery and unlawful entry with intent.

So more police, less crime? It’s not that simple

The next question is whether the high police numbers can take credit for these significant drops in crime. If that were the case, then one could assume that more police on the beat would drive crime down even further. The evidence for this argument, however, is scant.

It is well accepted that a combination of factors other than police strength can accurately predict crime trends. The correlations between these factors and crime are well known to criminologists. They include education levels, employment levels, income levels, school-leaving rates, the number of families that regularly need crisis assistance, and the heterogeneity of a relevant population. None of these factors is under the influence of police numbers, or indeed police powers.

Various commentators have explained the crime drop. The more reliable reasons are as follows: the better economic conditions in the West in the last three decades, better-financed social services, greater emphasis on intelligence-led policing, the removal of lead from petrol, and more affordable and available home alarms and business security services.

One could add higher imprisonment rates to the list, but that is a long bow to draw.

My preferred explanation (with regard to serious assaults at least) is a demographic one. The last of the baby boomers reached 40 years of age a decade ago, and most violent crimes are committed by men aged 18 to 35.

Is more police a cost-effective response?

The final question is this: if we are to outlay more than the A$10 billion we spend on policing, what are the opportunity costs? In other words, what has to be cut from government expenditures to cover the increase?

Employment projects, especially for Indigenous Australians, pre-release and rehabilitation schemes, diversion schemes, enhanced parole supervision, programs to prevent child abuse and neglect, and developmental educational schemes have each been shown to have a positive effect on crime prevention. Should we cut them?

Ironically, if we do, crime will increase and there will be greater pressure on governments to hire more police in response.

I don’t envy governments in setting their budgetary priorities, but some choices are better than others. Police are important, but not sufficient, in the crime-reduction effort. I have enormous faith in their abilities, but that doesn’t necessarily mean we need more of them.