Ben-- since all automatically reported payments appear to be equal, wouldn't it be more accurate to state that the reported payments are normalized over the loan period?
If you take into account that (hopefully) many loans use a "simple" interest calculation, one would expect the amount of principal paid to go up as the loan gets repaid. See for example
this post from Kendall Mau on the topic.
For example:
A $1000 loan, 12 months repayment, at 20% annual interest looks as follows. I assume that the auto-reported repayments would be $83.33, which is $1000/12, right?
Amortization Table for $1000.00 borrowed on Jan 1, 2007| Month/Year | 2/2007 | 3/2007 | 4/2007 | 5/2007 | 6/2007 | 7/2007 | 8/2007 | 9/2007 | 10/2007 | 11/2007 | 12/2007 | 1/2008 |
| Payment ($) | $92.63 | $92.63 | $92.63 | $92.63 | $92.63 | $92.63 | $92.63 | $92.63 | $92.63 | $92.63 | $92.63 | $92.63 |
| Principal Paid($) | $75.97 | $77.23 | $78.52 | $79.83 | $81.16 | $82.51 | $83.89 | $85.29 | $86.71 | $88.15 | $89.62 | $91.12 |
| Interest Paid($) | $16.67 | $15.40 | $14.11 | $12.80 | $11.47 | $10.12 | $8.75 | $7.35 | $5.93 | $4.48 | $3.01 | $1.52 |
| Total Interest($) | $16.67 | $32.07 | $46.18 | $58.99 | $70.46 | $80.58 | $89.33 | $96.68 | $102.60 | $107.08 | $110.10 | $111.61 |
| Balance($) | $924.03 | $846.80 | $768.28 | $688.45 | $607.29 | $524.77 | $440.89 | $355.60 | $268.89 | $180.74 | $91.12 | $0.00 |
Thanks,
--Ramón