year,zero_pct
1992,54.79897153263424
1993,54.12767327924735
1994,54.89735483610492
1995,53.27151645013812
1996,52.054279887956035
1997,48.094169741517604
1998,43.57023942311964
1999,41.08312655969622
2000,36.68198039921957
2001,27.33522257618643
2002,24.83111620055358
2003,28.158573650839248
2004,27.851826283813008
2005,25.866958836236588
2006,23.948249126928296
2007,22.345528100544577
2008,15.296868205637404
2009,21.164307468450133
2010,23.78784304351857
2011,20.64892731042033
2012,23.562693190683696
2013,22.80443214464177
2014,19.66312646601236
2015,17.544973168255655
2016,17.747052560120096
2017,19.020897735997817
2018,14.58591351116157
2019,15.698163359381152
2020,11.127211948536662
2021,11.700495205248172
2022,10.490540029462899
2023,13.418406268941007
2024,13.27005213730639
2025,11.611776771156848