OK... now that I've learned that the pop-up help topics do not appear to get indexed and can't be searched...
I agree that the calculation RichardF quoted from Kiva's own help topics does not appear to match the way that Default Rate is actually calculated on the site.
That said (and to prevent any throwing of rotten tomatoes this might cause), I don't believe that this is part of a vast Kiva conspiracy to mis-inform the lender. This would appear to be a case where Kiva's right hand might not know what the left hand has been doing (or even why it may have been done).
In my opinion, the method used on the site would, in general, decrease the stated Default Rate in a manner that might be perceived to be in Kiva's advantage. By using the calculation given in the help topic in question, the default rate would, in general, be higher than reported today. This statement is true using my portfolio as an example.
(Another disclaimer: your mileage may vary based the total volume of loans made, total amount of loans successfully repaid to date, and the total amount of non-defaulted loans made but not yet paid back)

Any Kiva Staffers want to shed some light on this? I see that Fiona, Liz & Premal have all been keeping an eye on this topic - perhaps they can help with some clarification.