Let’s illustrate—by example—how the wrong inferences can be reached by using the scatterplot referenced by Steven Wolfers. Take California for instance. According to the US Census Bureau, Its 2016 population was estimated at 39,209,127. Of that—In the 2016 Presidential General Elections—4,483,814 people voted for Trump, 9,754,079 votes went to other candidates and 24,971,234 didn’t vote. According to the chart referenced by Wolfers—in 2010—52% of California’s population had passports. If we assume that the same rate holds for 2016, we can say that the number of passport holders is around 20,388,746. You can see these numbers represented graphically in the charts below.