USA and UK both had increase - that's strange. UK has imigration crisis going on, that could explain part of it at least, so I checked my country (Poland), and it also had small increase in 2016 as well, but it was minimal 503->514. The downward overall trend is pretty clear. Homocides per year. Population is ~36 000 000

    1999 1121
    2000 1158
    2001 1169
    2002 1007
    2003 928
    2004 790
    2005 720
    2006 816
    2007 789
    2008 748
    2009 729
    2010 702
    2011 684
    2012 566
    2013 603
    2014 551
    2015 503
    2016 514