If we take the Hubbert's peak theory and make it analogous to Prosper, what we should be counting are not borrowers (consumers:cars and factories and utilities) or endorsers (advertisers/salespeople like gas station attendants) but lenders (who supply the product).
Hubbert says that when half the amount of oil produced has been produced, production has peaked and there is a precipitous, bell-shaped curve.
How can we measure this peak for Prosper? Do, for example, the number of current lenders outnumber ex-lenders?
Should we look at loans originated? Amounts bid? Those graphs seem to suggest a plateau but not a dropoff. (Yet?)