There's no single, globally agreed-upon statistic for the percentage of the world's population holding doctorate degrees. Data collection on educational attainment varies significantly across countries, and many developing nations lack comprehensive data. Furthermore, the definition of a "doctorate" can differ slightly between countries.
While precise figures are unavailable, it's safe to say the percentage is very small, likely in the low single digits or even less than 1%. The vast majority of the world's population does not hold a doctorate.