National Council on Pet Population Policy and Study does some really interesting work. Here's some of their past publications...
* Understanding Animal Companion Surplus in the United States: Relinquishment of Nonadoptables to Animal Shelters for Euthanasia. Journal of Applied Animal Welfare Science, 4(4), 237-248. 2001, Phil Kass.
* Characteristics of Shelter-Relinquished Animals and Their Owners Compared With Animals and Their Owners in U.S. Pet-Owning Households. Journal of Applied Animal Welfare Science, 3(3), 179-201. 2000, John C. New, Jr.
* Behavioral Reasons for Relinquishment of Dogs and Cats to 12 Shelters. Journal of Applied Animal Welfare Science, 3(2), 93-106. 2000, Mo D. Salman.
* Moving: Characteristics of Dogs and Cats and Those Relinquishing Them to 12 U.S. Animal Shelters. Journal of Applied Animal Welfare Science, 2(2), 83-86. 1999, John C. New, Jr.
Currently, they are conducting studies on the population dynamics of free-roaming cats and shelter indices that also reflect community health.
Photo by Murfomurf.