Extraction Rates of Flour
It has just become clear to me that extraction rates of flour are not always comparable.
When someone says that straight flour (white flour, AP flour, whatever) is about 72% extraction, that means 72% of the whole grain was kept as flour. 28% was tossed out as animal feed, including the bran, germ, and some wasted endosperm.
On the other hand, when talking about patent flour and clear flour, the percentages are not of the whole grain, but of the straight flour. So patent flour of 85% extraction is 85% of the straight flour (which was 72% of the grain). So that's actually only 61% of the whole grain.
This link describes it in more detail: http://www.theartisan.net/flour_descriptions_and_definitions.htm
Here is another page about it: https://bakerpedia.com/ingredients/straight-grade-flour/
Here it is visually:
Here are several links that use %-of-whole-grain when talking about extraction: