I used the topic with the specific crime of Murder and Nonnegligent manslaughter within the last twenty years. Can you help me find a null hypothesis and an alternative hypothesis?

Year	Murder and Nonnegligent Manslaughter
1997	18,208
1998	16,974
1999	15,522
2000	15,586
2001	16,037
2002	16,229
2003	16,528
2004	16,148
2005	16,740
2006	17,309
2007	17,128
2008	16,465
2009	15,399
2010	14,722
2011	14,661
2012	14,856
2013	14,319
2014	14,164
2015	15, 883
2016	17,250