for i in 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20; \
do echo "20$i posts count:"; ll source/_posts | grep " 20$i-" | wc -l;\
done

2001 posts count:
       1
2002 posts count:
       0
2003 posts count:
       0
2004 posts count:
       0
2005 posts count:
       5
2006 posts count:
      44
2007 posts count:
      39
2008 posts count:
      20
2009 posts count:
      16
2010 posts count:
      30
2011 posts count:
      95
2012 posts count:
     114
2013 posts count:
      65
2014 posts count:
      45
2015 posts count:
      62
2016 posts count:
      69
2017 posts count:
     114
2018 posts count:
      77
2019 posts count:
      62
2020 posts count:
       2