This discussion is something I've been studying for years.
What Bucky said was correct, the intent and actually worked... for a bit.
But because humans are involved, corruption has taken over. More hunting license are being granted than were ever supposed to be, by people accepting bribes. Poachers are also using the guise of trophy hunting and officials are skimming from the funds, so the proper amount is not reaching conservation efforts.
Figures are being faked, such as Botswana now claiming any elephant that crosses their border, as being part of their population.
Botswana claims annual increase for a total of 237,000 but the real number appears to be closer to under 132,000.