How Many Descendants Might Your Ancestors Have - Chart Included

I have one large family example and one small family example that are pretty good going back.  My goal is to determine a way to approximate how many descendants a degree of great-grandparent might have.  They obviously will vary and I am sure my families are not the absolute lower and upper bounds and my sample size is 2 lines and 8 generation differences.  So the small sample size makes this example very inaccurate as a true average, but it could be the basis to build a better sample size. 

This sample uses my Miley and Schmitz lines, again, one family line for the last 5 generations has been fairly small, and other family line for the last 5 generations has been fairly large.

The data:

Miley Line:

Generation and descendant count, with a percentage of each generation to the last:

Miley - person: descendants: percent

·       Gary:10 (my dad)

·       Dick: 16 : 160%

·       GLS: 48 :300%

·       James Jr: 80: 166%

·       James Sr : 199 :249%

Schmitz- - person: descendants: percent

·       Darlene: 10 (my mom)

·       Don: 51 : 510%

·       JWS: 72 : 141%

·       Phil: 186 : 258%

·       Nik: 391 :210%

We can now see our percents vary wildly and the percents between generations descendant counts range from 510% to 160% in our example.  This is a large swing, but notice that the numbers do not appear to be progressive and the percentage numbers do not appear to be exponential while the descendant counts clearly are.  This means that an average should be possible but realize our sample size is only 8.

Our set:  160%, 300%, 166%, 249%, 510%, 141%, 258%, 210%

Average:  249.25%

Meaning, in my example each generation’s descendants is best guessed as 249.25% of the previous generation.

We can extrapolate this to X generations to get a very rough guess at how many there might be:

Generations and descendant count guesses based on my small example:

1 (my dad)	10
2 ( gpa)	24.925
3 (gr-gpa)	62.1255625
4	154.8479645
5	385.9585516
6	962.0016898
7	2397.789212
8	5976.489611
9	14896.40035
10	37129.27788
11	92544.72513
12	230667.7274
13	574939.3105
14	1433036.231
15	3571842.807
16	8902818.196
17	22190274.35
18	55309258.83
19	137858327.6
20	343611881.6

Anyone Have Ideas on Trying to Collaborate with Germans?

There are a lot of Germans who do great genealogy and have created masterful works and completed amazing projects, but they don't always like to help you with yours, even if the person you are asking is the resident expert in the area or wrote the local Famlienbuch.  I have even tried to offer them hundreds of dollars in advance and really don't have much luck with them. 

Most recently I have had the author of a book lie to my face saying he didn't write the book.

I hate to believe that they are that much of a pain to work with.... Does anyone have any ideas on how to better approach German people for genealogy help?