Article History
Received: 21 April 2017
Accepted: 19 April 2018
First Online: 26 April 2018
Compliance with Ethical Standards
:
: The authors declare that they have no conflict of interest.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
: Informed consent was not obtained by the authors, since the data used in this study is made publically available by the National Center for Health Statistics and does not include identifying information.