I do not believe that data is compiled and even if they did, it would be pretty hard to make decent comparisons given the many variables involved. I think the typical expectations for a new career track pilot are to teach for around 2 calendar years before moving on. As a sort of minimum, you can expect at least a year of flight instruction simply by assuming an average of 75 flight hours a month then dividing the number of hours.

1200 hrs Part 135 mins - 300 hrs to begin = 900 hrs / 75 hrs per month= 12 months

However, I think 75 hours a month of air-time is pretty optimistic. It assumes you can both find a job and and get in the air an awful lot and it usually doesn't happen like that. If you could get half those hours (35) a month you would be doing well, and you would be done in 2 years. To even do this much flying, you would have to fly every single day of the month for 2 hours. That's not bad, but you have to remember that would only cover half the job, you have other duties to perform, and the time builder pals of mine who tried to pack the schedule flying 4 or more hours per day were completely sick of teaching within a few months.