Ice Cream Sales Lead to Higher Homicide Rates: How Correlation Doesn’t Always Equal Causation

A topic discussed in classrooms for years has been the strong positive correlation between ice cream sales and homicide rates. When ice cream sales rise, so does homicide. So does this mean ice cream causes us to commit violent crime? Of course not.

There is plenty of evidence to show that rising temperature causes an increase in crime,* most likely due to the fact that we’re more likely to lose our temper when trapped in hot weather. We’re also more also likely to gather and drink in the summer after work, filling the streets with more opportunity for crime in the evenings. Ice cream is always more appealing when it’s warm outside, so it stands to reason that sales are understandably higher in summer months. Both ice cream sales and crime rates soar in the summer, but the two variables are completely unrelated to one another.

What does this data mean for your firm?

The ice cream/homicide fallacy is discussed in classrooms for a good reason: It proves correlation does not necessarily equal causation. When two or more variables correlate, you may be tempted to conclude that the correlation is due to a relationship between the variables. In this instance, there’s no connection between ice cream and homicide at all: the causation is actually between temperature and ice cream, and temperature and homicide.

Correlation and causation is vitally important for law firms to consider. For example, divorce attorneys are usually busiest in January, because January is the most popular time for partners to break up. Whether it’s due to a bad vacation or wanting a “fresh start,” a survey of 1,881 British couples found that 21% of breakups happen in January, far and away the worst month of the year for relationships.

If a divorce law firm starts running a new PPC campaign and sees a huge spike in signed clients in January, it may incorrectly attribute the increase in cases to the new marketing campaign. In this situation, it’s more likely that a divorce firm’s caseload would increase in January regardless of running campaigns. Could the PPC ad have positively affected the firm’s signed cases? Absolutely. But without looking at hard data from the campaign, it’s impossible to draw conclusions from only the positive correlation between new clients and PPC spending.

Personal injury attorneys may also see an increase in claims during the holiday season: According to the National Institute on Alcohol Abuse and Alcoholism, 40% of fatal car crashes over Christmas and New Year’s are due to drunk drivers. Much like the rise of ice cream sales and homicides, it’s likely that a lot of people will be filing personal injury claims after New Year’s Eve regardless of how much your firm is spending in advertisements.

How can you positively identify the causation of data?

You should be aware of any seasonal changes you see over the years at your firm. For example, Social Security firms likely saw an increase in applications around 2009, because most Baby Boomers were turning 60-65, which is statistically the best age to apply for disability benefits. The US recession also started at the end of 2007, which led to workers losing their jobs and turning to Social Security. Forecasting when your potential clients will be looking for an attorney can go a long way in evaluating your campaigns and marketing efforts.

As an attorney, the most important thing you can do to truly evaluate your firm’s efforts is asking every caller or walk-in claimant how they heard about your firm. This will give you key insights as to how word is spread about your services from campaigns that cannot be monitored online, such as TV ads or billboards.

Finally, you can attribute conversions by using online software if your firm utilizes any web marketing channels. Free tools like Google Analytics can help you pinpoint which channels a consumer uses to reach your site, and at what point a consumer chooses to contact your firm. You can even use case management software to run reports on your pending cases. These reports can show you your success by source from which you received a lead, attorney handling the case, and more.