Actually.Zach has seen concerts during 13 years.

Year   Concerts Seen  
2021 3 concerts
2020 8 concerts
2018 16 concerts
2017 44 concerts
2016 37 concerts
2015 26 concerts
2014 13 concerts
2013 9 concerts
2012 7 concerts
2011 4 concerts
2010 5 concerts
2009 2 concerts
2008 3 concerts