Accessory Dwelling Unit application rate data?

Hello,

I am looking for data on rates of applications for accessory dwelling units where permitted as a limited use (by right but with conditions). The only information I've come across so far is a reference to a national survey of 47 communities finding that with "favorable" zoning, ADU applications rates were 1 per 1,000 single-family homes per year (Accessory Units: An Increasing Source of Affordable Housing. 1991. By Patrick H. Hare and John Danbury. Public Management 73, cited in the
1995 MRSC report "Accessory Dwelling Units").

Is anyone aware of more recent data, or could anyone report out on their own community's experience?

Thanks,
~Ann Dillemuth
Research Associate
American Planning Association
adillemuth@planning.org