Credit analysis, Reduced Form Models

Hey guys,

I’m a little confused. CFA book 5 page 414 says: "It can be shown that this maximum likelihood estimation is equivalent to running the following simple linear regression to estimate the coefficients:

ln (d / (1-d)) = a + ∑bx, where the dependent variable includes the default flag (d = 1 if default, 0 if no default).

This is called a logistic regression…"

Is it ok that if d equals 1, we divide 1 by 0? Or am I missing something?

Thanks

The given model is for the ln(odds) for default (probability of d, default, is between 0 and 1). For example, if the probability of default is 0.8, then the value of your DV would be Ln[0.8/(1-0.8)]= Ln(4).

They’re also explaining that when you enter data, a default is coded as a 1, and no default is coded as 0.

Hope this helps.

Oh, I see… I think I got it now. Thanks for a quick response!

Glad to help.