Tomado de Democracy as an Equilibrium de Adam Prezeworski

"No democracy ever fell in a country with a per capita income higher than that of Argentina in 1975, $6055. This is a startling fact, given that throughout history about 70 democracies collapsed in poorer countries. In contrast, 35 democracies spent about 1000 years under more developed conditions and not one died. Developed democracies survivedwars, riots, scandals, economic and governmental crises, hell or high water."

"The probability that democracy survives increases monotonically in per capita income. Between 1951 and 1990, the probability that a democracy would die during any particular year in countries with per capita income under $1000 was 0.1636, which implies that their expected life was about 6 years. Between $1001 and 3000, this probability was 0.0561, for an expected duration of about 18 years. Between $3001 and 6055, the probability was 0.0216, which translates into about 46 years of expected life. And what happens above $6055 we already know: democracy lasts forever."

"The probability that democracy survives increases monotonically in per capita income. Between 1951 and 1990, the probability that a democracy would die during any particular year in countries with per capita income under $1000 was 0.1636, which implies that their expected life was about 6 years. Between $1001 and 3000, this probability was 0.0561, for an expected duration of about 18 years. Between $3001 and 6055, the probability was 0.0216, which translates into about 46 years of expected life. And what happens above $6055 we already know: democracy lasts forever."