Regime Durability: The number of years since the most recent regime change (defined by a three point change in the p_polity score over a period of three years or less) or the end of a transition period defined by the lack of stable political institutions (denoted by a standardized authority score). In calculating the p_durable value, the first year during which a new (post-change) polity is established is coded as the baseline ``year zero'' (value = 0) and each subsequent year adds one to the value of the p_durable variable consecutively until a new regime change or transition period occurs.