Final answer:
The indigenous population of central Mexico declined by about 4) 75% between 1519 and 1605, as diseases brought by Spaniards devastated the Aztec heartland from around 25 million to under 2 million.
Step-by-step explanation:
Between 1519 and 1605, the indigenous population of central Mexico declined by about 75%. The population of the Aztec heartland dropped from about 25 million on the eve of the Spanish conquest in 1519 to just under 17 million a decade later.
After twenty years, the population was reduced to approximately 6 million, accounting for a 75% decline. By 1580, there were less than 2 million people left from the original 25 million.