An official website of the United States government
The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before
sharing sensitive information, make sure you’re on a federal
government site.
The site is secure.
The https:// ensures that you are connecting to the
official website and that any information you provide is encrypted
and transmitted securely.
Kusunoki Y, Upchurch DM.Kusunoki Y, et al. Among authors: upchurch dm.Demography. 2011 Nov;48(4):1451-72. doi: 10.1007/s13524-011-0061-0.Demography. 2011.PMID: 21887582Free PMC article.