Commenter JBS points out that total births in Arizona from January to August in 2008 have declined from the same time period in 2007 by 2.9%:
Prelimary birth data out of Arizona indicates there may have been a drop in the number of births to illegal alien Hispanics when Arizona's crackdown on illegals began in 2007 and just now having an effect in 2008.The Arizona Department of Health Services has comparable data going back to 1996. Of special interest are the numbers for '06, '07, and '08.
Comparing January-August of 2007 to January-August 2008, there has been a 2.9% dip in the absolute number of total births in Arizona in 2008 - the first time there has been an absolute drop in the number of births in Arizona since at least 1996 (Warning, these numbers for 2008 might be subject to change, but I thought a 2.9% drop in overall births was big enough not to be statistical noise).
The birth totals are reported by county. There is no 'smoking gun' association between the percentage of a county's population that is foreign-born and the year-over-year change in total births, even when population growth from previous years* is controlled for. The weighted correlation between the change in total births from '07 to '08 is an almost non-existent .03, without any statistical significance. Similarly, there is no meaningful relationship between the percentage of a county's population that is Hispanic and birthing changes.
I am not sure how much this tells us one way or the other. Maricopa county, home to more than 60% of Arionza's population, did show a larger year-over-year absolute decrease in births (4.3%) than the state as a whole (2.9%) did. Nearly one-third of the county's residents are Hispanic and nearly 15% are foreign-born.
Is there more angst among illegals on Joe Arpaio's turf? Most counties showed a very marginal decrease in births, and five of the 15 actually saw an increase. The decrease in Maricopa is what brings the entire state's total down from the same eight month period the year before. Pinal county, between Phoenix and Tucson, experienced the greatest year-over-year increase in births (10.6%). I'm too unfamiliar with Arizona to offer any insight, but maybe some readers will be able to.
* Growth rates are based on Census population figures from '00 to '06.