Is there a correlation between searches for “Formula E” and “Electric vehicles” on Google?

First we download a data files from Google Trends - us-searches, containing searches for the US only. I think this is the data used in the graphic shared.

# read in the US data
usSearches <- read.csv("raw_data/us-searches.csv")
names(usSearches) <- c("month", "fe", "electric")

# Let's take a quick look at the data
head(usSearches, 10)
##      month fe electric
## 1  2004-01  5       27
## 2  2004-02  7       37
## 3  2004-03  9       39
## 4  2004-04  8       57
## 5  2004-05 13       72
## 6  2004-06  4       53
## 7  2004-07  3       37
## 8  2004-08  4       35
## 9  2004-09 10       39
## 10 2004-10  9       39

As you can see from the output above, we have a dataset containing 2 variables - “fe” (monthly search volumes for ‘Formula E’) and “electric” (monthly search volumes for ‘Electric Vehicles’). There are 157 observations in total, to cover the period from 2004 - date.

Checking for a correlation

Now, we can use R to examine the correlation between our 2 variables.

# What is the correlation between the two searches?
cor.test(usSearches$fe, usSearches$electric)
## 
##  Pearson's product-moment correlation
## 
## data:  usSearches$fe and usSearches$electric
## t = -3.5988, df = 155, p-value = 0.0004295
## alternative hypothesis: true correlation is not equal to 0
## 95 percent confidence interval:
##  -0.4162292 -0.1265632
## sample estimates:
##        cor 
## -0.2776961

None, really. What we care about above is the final number output(-0.278), which tells us there’s a correlation of -0.278 between the two, suggesting that when searches for one term increase, searches for the other decrease.

What about after June 2014, shortly before Formula E began?

# Filter the data to include only data after June 2014
recentUS <- usSearches %>% filter(month >= "2014-06-01")

# What is the correlation between the two searches?
cor.test(recentUS$fe, recentUS$electric)
## 
##  Pearson's product-moment correlation
## 
## data:  recentUS$fe and recentUS$electric
## t = 1.8912, df = 30, p-value = 0.06829
## alternative hypothesis: true correlation is not equal to 0
## 95 percent confidence interval:
##  -0.02518432  0.60609314
## sample estimates:
##       cor 
## 0.3263758

This time around, our correlation test tells us that the correlation is 0.326 (“medium”, according to Cohen’s rule of thumb). However, since the boundaries of our 95% confidence intervals include the number 0, we can’t say with any real confidence that the correlation is not 0.

TLDR: There does not appear to be any significant correlation between searches for Formula E and Electric vehicles.