The typical approach is to count the number of bug tickets resolved over a period of time. However, it doesn't factor in the size of the ticket. Let's say a bug that has been worked on for 2 hours versus a bug that has been in works for 3 days. Two tickets, but different size.
Quantify automatically calculates the time spent on every ticket so now you have consistent data to more precisely measure how much time was spent on bugs versus other tickets.
First, you need a very simple Jira filter that would return only bugs, just use the following JQL:
type = Bug
Then add it to the Quantify dashboard widget and you will see what percentage of all work has been spent on bugs per each individual.
Time spent on bugs by individual
You can group results by project
Time spent on bugs by project
Next step is to look at the trend over time to understand the dynamic. It will be covered in another article.