Thanks to OnTheFence for filling me in about this discussion

I think Investar & Ira summed up the purpose of that chart exactly. As for Fred93's comment about it being "misleading" or "highly skewed toward younger loans", I think that's a bit overstated. The chart purposefully only includes loans originated before Jan, 2007 to minimize this effect. So the denominator is in fact the same for the first 27 months (as you can see from the data below the chart).
The data may be somewhat inaccurate because not all the loans have completed yet (as I mention in the summary), but I'm pretty confident that the overall trend shouldn't deviate much from what you see in that chart. If Fred93 could explain to me his reasoning for thinking that the final results will be significantly different than what I currently show there, I would be interested to hear that.
The original purpose for that chart was to help with pricing risk in the secondary market (if one ever comes along). The idea being that you could use that chart as a guide to help you figure out how much risk has been "baked out" of a loan at a certain age. For example, a loan that has already made 12 on-time payments should be perceived as somewhat less risky than a brand new loan. Using my chart, you would be able to quantify that risk - after 12 on time payments, the default risk should have decreased by about 70%. If you used Fred93's charts, it would be around 65% instead after accounting for differences in methodology (My "Late" vs. Freds "1+ late", Fred's use of current loan status vs. my use of "first month late").