does anyone here know stats? / the widely quoted Rental Vacancy Rate from Citi-Habitats

 
data point about rentals tracked down (it wasn’t hidden)
That NY Times piece from Sunday, Changing Course to Avert a Glut, addresses macro-level questions about plans to build lots of condominium in Manhattan. Among the data nuggets reported by Christine Haughney is the oft-quoted statistic from Citi-Habitats for the vacancy rate for Manhattan rental apartments.
 
“Converting projects to rental apartments is starting to make more sense because this sector has strengthened. The vacancy rate for rental apartments in Manhattan is a very low 0.8 percent, according to Citi Habitats, a Manhattan real estate brokerage. The borough hasn’t had such a small percentage of rental vacancies since before Sept. 11, according to Gordon Golub, Citi Habitats’ senior managing director of Citi Habitats.”
 
I don’t recall ever seeing any report about rental vacancies in Manhattan that were not sourced to Citi-Habitats.
 
small number, small sample?
I’ve got nothing against Citi-Habitats, but I am skeptical by nature and I am curious about that number, 0.8%. I have no reason to doubt it as accurate, but a number that small deserves a bit of scrutiny.
 
Citi-Habitats puts out a semi-annual market report focused mostly (but not exclusively) on rentals in Manhattan. I usually don’t pay a lot of attention to rentals but there is a lot of good stuff in The Black & White Reports, the most recent of which is for the last half of 2005.
 
the source in black & white
Page 5 of that B & W provides information for the rental vacancy statistic, which struck me as a little lean for an island with 564,721 rental households (as I discovered when I blogged earlier about this NY Times article). The stat is based on a “sampling of 8-10 key rental buildings in each Manhattan neighborhood below 100th Street”. They count 11 neighborhoods, so that is a minimum of 88 buildings surveyed, and a maximum of 110 buildings. If the average size rental building has 100 units, that is about 5,000 buildings units.
 
I have no idea, but is 110 buildings a large enough sample to be statistically significant? I suppose the number is self-validating to the extent that it is consistent over time, but I gotta wonder about that.
 
© Sandy Mattingly
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