How accurate are Themis's polls?

ELECTIONThemis POLLACTUAL RESULT
2019-03-31 İstanbul Belediye
Yıldırım: 48.3%
İmamoğlu: 49.3%
Yıldırım: 48.61%
İmamoğlu: 48.77%
2017-04-16 Anayasa Referandumu
Evet: 46.1%
Hayır: 53.9%
Evet: 51.41%
Hayır: 48.59%