My Collections Metrics Flawed

Oh fiddle-faddle. As Lend2 has pointed out, my method of tracking Prosper collections is a bit flawed. Prosper has confirmed that, indeed, loans don't just go current when payments are made. From deep within the inner workings of Prosper:

For the raw “Delinquency Activity” data he is looking at I think he’s assuming a loan has fewer options about how it can change state, aging or curing than it does. 3 month late loans can stay 3 months late for more than a month if a payment comes in before it rolls to 4+ months late. Loans that are 4+ months late can receive payments that partially offset the past due total resulting in the loan being becoming 3 months late. 2 month old loans can become 3 months late. Some payments can fail a couple weeks after they’re made so some loans that are 1 month late might jump to 3 months late…

D'oh. This blows my easy-to-use technique out of the water. If a 4+ month late loan can improve to 3 months (or 3 month improve to 2 month, and so on), it's very hard to tell the life cycle for a loan. Time for a plan C.