People who work with criminal justice and criminology data often encounter longitudinal variables. Longitudinal variables are measured repeatedly over time. Crime rates are often presented longitudinally as a means of determining trends. Line graphs can make it easy to discern trends.
Longitudinal variables: Variables measured repeatedly over time.
Trends: Patterns that indicate whether something is increasing, decreasing, or staying the same over time.
shows a line graph of data from the Uniform Crime Reports measuring the annual number of hate-crime incidents from 1996 to 2015. the annual percentage of all hate crimes that are motivated by sexual-orientation bias. Together, these two line charts show two trends. First, total hate-crime incidents have declined slightly in recent years. Second, despite the downward trend in total incidents, the percentage of incidents that are based on the victims’ sexual orientation has risen steadily, albeit with a small drop from 2011 to 2012.