Thanks for sharing this info. A few observations:

Most FGAs spent a lifetime being called on the carpet every time one of their kids screwed up, so the 18% (!) loss of 690 FGAs in 2005 is probably direct fallout due to Rick's suicide/murder.

I calculated the average rate of decline from 2000 to 2005 using your stats and those available at Xfamily. The six-year rate of decline is around 4%. Without any significant changes over the next 20 years (when the oldest SGAs will be middle-aged), the group will number less than 4,200.

However, there's a point at which the total losses to the adult population will be so great that it cannot sustain itself. Calculating this tipping point depends on how many young adults remain in the group. If what you're saying about the low number of SGAs making up the adult population is correct, TFI will very likely reach the tipping point in 5 to 10 years.

For the sake of simplicity, let's assume Peter's statistic of 1,000 SGA adults is correct. That figure represents a 748% loss of second generation members born into the group by 1988, according to 1999 census figures. Because the loss occurred over the last 18 years, it averages to 42% yearly decline in second generation membership.

The numbers suggest a simple conclusion: TFI is in deep doo-doo. No wonder they teach such bizaare shit. They're up to their necks in it right now, and Peter has to know it even if his math sucks.