Comparing Polity IV and V-dem

Polity IV 

All independent countries with a total population of 500,000 or more 

Time: 1800~

procedure: 5 experts respond to each indicator

Polity 2: it is fit for use in time-series analyses

Polity 2 與polity這兩個變數都介於-10到10，兩者最大的差異在於對於-77和-88的處理。Polity 中有三種特殊狀況-66 (外國佔領), -77(無政府狀態或是無人領導的情形), -88(轉型期間，可能是行政部門主導修憲、國際組織介入協調內戰雙方協商制憲等)。

Polity2

1)      把-77視作0

2)      在-88的處理上變成漸進的方式。

例如A國的polity變數1971是-7分à-7

         1972是-88分à-4

         1973是-88分à-1

         1974是-88分à+2

         1975是+5分à+5

Högström, J. (2013). Does the choice of democracy measure matter? Comparisons between the two leading democracy indices, Freedom House and Polity IV. Government and Opposition, 48(2), 201-221.