\begin{filecontents*}{StatistikWahlergebnisse.csv}
Jahr,Althyduflokkur,Framsoknarflokkur,Sjalfstadisflokkur,Althydubandalagid,Samtoek,Bandalag,Kvennalistinn,Borgaraflokkur,Samtoekumjafnretti,Thjodvaki,Frjalslyndiflokkurinn,Borgarahreyfingin,Samfylkingin,Vinstrihreyfingin,Bjoertframtidid,Piratar,Vidreisn,Mithflokkur,Sonstige
1963,14.2,28.2,41.4,16.0,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,0.2
1967,15.7,28.1,37.5,17.6,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,1.1
1971,10.5,25.3,36.2,17.1,8.9,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,2.0
1974,9.1,24.9,42.7,18.3,4.6,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,0.4
1978,22.0,16.9,32.7,22.9,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,5.5
1979,17.4,24.9,35.4,19.7,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,2.5
1983,11.7,19.0,38.7,17.3,nan,7.3,5.5,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,0.5
1987,15.2,18.9,27.2,13.3,nan,0.2,10.1,10.9,1.2,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan
1991,15.5,18.9,38.6,14.4,nan,nan,8.3,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,nan,2.9
1995,11.4,23.3,37.1,14.3,nan,nan,4.9,nan,nan,7.2,nan,nan,nan,nan,nan,nan,nan,nan,4.3
1999,nan,18.4,40.7,nan,nan,nan,nan,nan,nan,nan,4.2,nan,26.8,9.1,nan,nan,nan,nan,1.9
2003,nan,17.7,33.7,nan,nan,nan,nan,nan,nan,nan,7.4,nan,31.0,8.8,nan,nan,nan,nan,0.8
2007,nan,11.7,36.6,nan,nan,nan,nan,nan,nan,nan,7.3,nan,26.8,14.3,nan,nan,nan,nan,3.3
2009,nan,14.8,23.7,nan,nan,nan,nan,nan,nan,nan,2.2,7.2,29.8,21.7,nan,nan,nan,nan,0.6
2013,nan,24.4,26.7,nan,nan,nan,nan,nan,nan,nan,nan,nan,12.9,10.9,8.2,5.1,nan,nan,11.8
2016,nan,11.5,29.0,nan,nan,nan,nan,nan,nan,nan,nan,nan,5.7,15.9,7.2,14.5,10.5,nan,5.7
2017,nan,10.7,25.3,nan,nan,nan,nan,nan,nan,nan,nan,nan,12.9,16.9,1.22,9.2,6.7,10.9,0.2
\end{filecontents*}
\documentclass{scrartcl}
\usepackage[main=ngerman,icelandic]{babel}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{pgfplots}
%\pgfplotsset{compat=1.15}
\usepackage{rotating}
\begin{document}
%\begin{sidewaystable}
\begin{tikzpicture}
\begin{axis}[
enlargelimits=false,
xlabel={Jahr},
ylabel={\%},
xtick=data,
minor xtick={1963,1967,1971,1974,1978,1979,1983,1987,1991,1995,1999,2003,2007,2009,2013,2016,2017},
grid=minor,
xticklabel style={
rotate=90,
anchor=east,
/pgf/number format/1000 sep={},
