You think Biden's old?

Whoever wins the US election in November and takes office in January will be the oldest president ever inaugurated. Trump was the oldest president to win a first term in 2016, and if he wins a second term he'll by 74 at his 2021 inauguration. If Biden wins, he'll be 78. 

That's pretty old! But septuagenarian presidents are a common occurrence in Africa. When Robert Mugabe was forced from office at age 93 he was the oldest head of state in the world. 

I posted the ages of all the presidents in ECOWAS countries two years ago. Five out of 15 were 70 years or older. Todd Moss and Stephanie Majerowicz of the Center for Global Development speculated that large gaps could lead to public anger, protests, and government turnover. We can test that hypothesis over the past two years. Below is the list from 2018; if the president hasn't changed I just posted the new age, and if he was recently re-elected. If the president did change, I post the new president with his new age, and I also included the age gap from 2018. In 2018 I only did the age gap for the oldest 5 presidents. 

1. Liberia: George Weah, was 51, now 53
2. Togo: Faure Gnassingbé, was 52, now 54 (re-elected to a fourth term in 2020)
3. Gambia: Adama Barrow, was 53, now 55
4. Sierra Leone: Julius Maada Bio, was 54, now 56
5. Senegal: Macky Sall, was 56, now 58 (re-elected to a second term in 2019)
6. Benin: Patrice Talon, was 60, now 62
7. Guinea-Bissau: José Mário Vaz, was 60 (minus media age 19 = 41 year gap; lost re-election in 2019). New president: Umaro Mokhtar Sissoco Embaló, age 47. 
8. Burkina Faso: Roch Marc Christian Kaboré, was 61, now 63
9. Cape Verde: Jorge Carlos de Almeida Fonseca, was 67, now 69
10. Niger: Mahamadou Issoufou, was 67, now 69
11. Mali: Ibrahim Boubacar Keïta, was 73 (minus median age 16 = 57 year gap), overthrown in a coup last week. 
12. Ghana: Nana Addo Dankwa Akufo-Addo, was 74 (minus median age 20 = 54 year gap), now 76
13. Nigeria: Muhammadu Buhari, was 75 (minus median age 18 = 57 year gap), now 77. Re-elected for a second term in 2019. 
14. Cote d'Ivoire: Alassane Dramane Ouattara, was 76 (minus median age 18 = 58 year gap), now 78. Running for a 3rd term; taking advantage of a new constitution to circumvent a two-term limit. 
15. Guinea: Alpha Condé, was 80 (minus median age 19 = 61 year gap), now 82. Running for a 3rd term; also taking advantage of a new constitution to circumvent a two-term limit.

Conclusions: ECOWAS presidents are still really old. Only one (was close to the median) was replaced with a younger (the youngest in the region, in fact) president. 

Being younger/closer to the median age seems to help little if at all to win re-election. Four presidents faced re-election; the two younger incumbents won, the close-to-median age (among the presidents) incumbent lost and the older incumbent (one of the five over 70) won. 

One of the other septuagenarians was overthrown in a coup last week, which suggests risk for large age gaps. But the oldest two presidents are running for third terms despite 2-term limits in their countries. Perhaps they are miscalculating, or perhaps incumbency advantage (Bleck and van de Walle, p. 77) matters more than age gap.