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.
Thehttps://确保你连接到官方的我们bsite and that any information you provide is encrypted and transmitted securely.
Table representation of search results timeline featuring number of search results per year.
| Year | Number of Results |
|---|---|
| 1975 | 1 |
| 1976 | 1 |
| 1977 | 1 |
| 1978 | 1 |
| 1979 | 2 |
| 1980 | 3 |
| 1981 | 1 |
| 1982 | 2 |
| 1983 | 1 |
| 1984 | 2 |
| 1985 | 3 |
| 1986 | 3 |
| 1987 | 2 |
| 1989 | 1 |
| 1990 | 2 |
| 1991 | 1 |
| 1992 | 2 |
| 1993 | 1 |
| 1994 | 2 |
| 1995 | 1 |
| 1998 | 1 |
| 1999 | 1 |
| 2000 | 4 |
| 2001 | 1 |
| 2002 | 3 |
| 2003 | 3 |
| 2005 | 3 |
| 2006 | 1 |
| 2007 | 2 |
| 2008 | 5 |
| 2009 | 2 |
| 2010 | 1 |
| 2011 | 3 |
| 2012 | 4 |
| 2013 | 6 |
| 2014 | 2 |
| 2015 | 5 |
| 2016 | 5 |
| 2017 | 1 |
| 2018 | 5 |
| 2019 | 9 |
| 2020 | 3 |
| 2021 | 8 |
| 2022 | 8 |
| 2023 | 5 |