US President Donald Trump, 74, is running for reelection against former Vice President Joe Biden, who will turn 78 soon after the November election. They are the oldest candidates for president in US history — and both are more than 35 years older than the median age for Americans in 2020. So, is the White House unique in becoming a gerontocracy? We look at the age gap between country leaders (presidents and prime ministers) and their populations, across the G20 group of the world's largest economies.