Statistical summary

Majoritarian System and Presidential System: 10/18 = 55%
Majoritarian System and Parliamentary System: 2/18 = 11%
Majoritarian System and Semi-Presidential System: 6/19 = 31.5%
Proportional System and Presidential System: 6/11 = 54%
Proportional System and Parliamentary System: 3/11 = 27%
Proportional System and Semi-Presidential System: 1/10 = 10%
Proportional System and Monarchical System: 1/10 = 10%
Proportional System and Nomination and Presidential System: 1/7 = 14%
Mixed System and Presidential System: 1/6 = 17%
Mixed System and Parliamentary System: 2/6 = 33%
Mixed System and Semi-Presidential System: 2/6 = 33%
Mixed System and Directorial System: 1/6 = 17%
Majoritarian and Nomination System and Presidential System: 6/16 = 10%
Majoritarian and Nomination System and Parliamentary System: 4/16 = 25%
Majoritarian and Nomination System and Semi-Presidential System: 6/16 = 38%
Majoritarian and Nomination System and Monarchical System: 1/16 = 6%
Proportional and Nomination System and Parliamentary System: 3/6 = 50%
Proportional and Nomination System and Semi-Presidential System: 3/6 = 50%
Nomination System and Presidential System: 1/21 = 5%
Nomination System and Parliamentary System: 14/21 = 67%
Nomination System and Semi-Presidential System: 1/21 = 5%
Nomination System and Monarchical System: 5/21 = 24%
Majoritarian, Proportional, and Nomination System and Presidential System: 1/2 = 50%
Majoritarian, Proportional, and Nomination System and Semi-Presidential System: 1/2 = 50%
Without an Upper House and Presidential System: 33/112 = 29%
Without an Upper House and Parliamentary System: 40/112 = 35%
Without an Upper House and Semi-Presidential System: 34/112 = 30%
Without an Upper House and Monarchical System: 5/112 = 4.4%