Final answer:
To provide an overview of 'shall-issue' gun laws over time, a numeric dummy variable is created to represent the presence of such laws in each state. The fraction of states with these laws each year is then calculated and visualized using a line graph, allowing for an easy comparison of changes across states and over time.
Step-by-step explanation:
To create a figure showing the fraction of states with 'shall-issue' laws over time, you would first need to define the numerical dummy variable. Let's call this variable 'shall_issue_dummy'. This variable will take the value of 1 if the state has a shall-issue law at a given time, and 0 if it does not. Once you have this data, you can calculate the fraction of states with shall-issue laws by summing the dummy variable values for all states and then dividing by the total number of states.
For instance, if you're looking at data for the year 2000 and 25 out of 50 states have shall-issue laws, your fraction for that year would be 25/50 or 0.5. This indicates that 50% of the states had shall-issue laws at that time. To visualize changes over time, you could then create a line graph with the years on the x-axis and the fraction of states on the y-axis, plotting each year's data point accordingly. This would provide a clear overview of how the prevalence of shall-issue laws has evolved across different states over the years.