Insulation of leaders can be summarized by the legislative majority required

Evidence

The third important element is the degree of insulation, captured by the parameter M which we view as a “summary statistic” for a wide variety of institutional rules that limit the power of appointed leaders. The most direct interpretation of M refers to the question of what majority a government has to command to pass legislation. — Philippe Aghion, Alberto Alesina, and Francesco Trebbi, Endogenous Political Institutions, 45

Categorization

• DEFINE: Defines the parameter M as a summary statistic for institutional rules constraining appointed leaders, with majority thresholds as its most direct reading.