Bestandslücken
[N=1995,50; 1996,21u.42-43; 1997,42; 1998,33u.52; 1999,1 ;2000,14-15u.45u.51; 2001,6u.20-21; 2004,44; 2005,48; 2007,9-10; 2009,39; 2010,3; 2012,37; 2013,14; 2014,27; 2015,9u.11u.14; 2016,1u.16u.18u.45; 2017,14u.17-18u.26u.33u.43u.50u.52; 2018,1u.13u.29u.40u.43-52; 2019,10-13u.17u.22u.27u.37; 2020,5u.29-52]