Political Constraint Index (POLCON) measures the degree of checks and balances.
Constructed by Witold Henisz.
Downloadable from Henisz's website.
Annual panel for all countries in the world since 1800.
Variables used to construct the POLCON index are also included in the dataset: the existence of an effective lower legislative chamber (based on Bank's CNTS data in the 2002 version; based on POLITY in the 2005 version), the existence of effective second legislative chambers, the existence of an independent judiciary (based on POLITY and ICRG), the existence of independent sub-federal entities, etc.
I am not sure if it is a good idea to use POLITY's executive constraint variable to obtain the existence of an effective lower legislative chamber or an independent judiciary.
Used by Keefer and Stasavage (2003).