Fun with Numbers
September 21st, 2007
Today’s exercise looks at Exodus’ retention rates. Let’s assume, for the sake of this exercise, that the sample used by Yarhouse and Jones is representative of all new Exodus participants and see what it tells us.
To start we know that 98 participants started in the study (point A) and that at some point 30 to 48 months later (point C) there were only 73. We’ll take three years as our point C for the simplicity of math. Further, we know that at the midpoint (point B) there were 85.
This tells us that between point A and point B there was a retention rate of 86% (85/98) and that between point B and point C there was also a retention rate of 86% (73/85).
But wait. We also know that of the 98 participants, 57 were new and 41 were one to three years into the program. Just for fun, let’s apply our retention rates backwards to see if we see anything about these participants.
If we assume the same retention rates, the 41 would have been 48.2 a year and a half before and 56.7 at three years back.
Wow, that’s the same as the current size sample. Perhaps a coincidence? Or perhaps this suggests that there is a consistent drop off rate of 15% every year and a half that continues for at least four years. This translates into roughly a 91% retention rate per year.
Now let’s make some guesses about how many new participants there are each year in Exodus programs.
The researchers claim that not all Exodus ministries were willing to cooperate. Even after pressure from Yarhouse and Jones and, presumably, Exodus national. So let’s suppose that only a third of new Exodians participated in the study.
Well then, in any given year there would be about 171 new Exodians. With a 91% retention rate, the following six years would show retention of these Exodians of 156, 142, 129, 117, 106, and 96. Let’s charitably assume that after six years there is no longer any drop off at all.
Obviously each new year brings more Exodians to count up. There would be 171 new participants and 156 hold overs from the previous year along with 142 from the year before that. And so on.
Also, we have to assume that these participants will some day die. Since the average age of participants was listed at 37.5 years, let’s assume they’ll live for another 40 years to the ripe old age of 77.
So let’s see how many years it would take to reach Alan Chambers’ favorite number of “hundreds of thousands”.
OH NO!!! We can’t get there!! It turns out that with the above assumptions, the number of Exodians participating in Exodus ministries plateaus in its 39th year at 3,989. (Thank God we stopped dropping off in the sixth year or it would plateau at 1,854).
Oh gosh!! Well, maybe Yarhouse and Jones got less than 1/3 participation. Maybe only one out of ten Exodians joined the study and maybe really each year there are 570 new recruits. Ah, that’s much better. The peak participation rises to 13,430.
But that’s still a far cry from “hundreds of thousands”. In order for there to be 100,000 participants ever at Exodus, with a 91% annual retention rate for six years after which there is NO drop off, and a 40 additional year life expectancy (and participation), Exodus would have to have 4,249 new participants each year, or an average of 28 new participants each year in each of Exodus’ 150 affiliates (news reports suggest that the total membership in any given group is in the single digits).
Which would mean that Yarhouse and Jones’ study used a 1.3% population sample of 57 and called it representative. Or, alternately, that Chambers’ claims of “hundreds of thousands” is nothing more than a figment of his imagination. You do the math.