Is initial *b really rare?

We always hear that PIE initial *b is rare but I don't quite see the
basis for it. I've recently begun analyzing phoneme frequencies in
PIE (using a summary of Pokorny I found on the net). In analyzing
initial vowels and consonants (I have not yet differentiated between
the two but I will expand my analysis later today) I constructed a
98% confidence interval and found that b frequencies occurs
comfortably within that interval. Other sounds occur much more
infrequently yet no one says boo about them (well, except unvoiced
aspirated stops). So what statistical basis do people have for saying
that initial *b is rare?

I'm wearing flame retardant underwear in anticipation of Glen's
reply :)


Etherman