According to the National Institute of Indigenous Peoples ("Instituto Nacional de los Pueblos Indígenas", or INPI in Spanish) and the INEGI (official census institute), in 2015,25,694,928 people in Mexico self-identify as being indigenous of many different ethnic groups, which constitute 21.5% of Mexico's population. At the time of Spanish conquest in the late 15th century, the indigenous population of Mexico has been estimated at about 25 million, and has therefore only reached this figure again over 500 years later."" These modern figures however are language based, making numbers under reported, as it discounts Indigenous people who can only speak Spanish. Due to the extreme success of "mestizaje" nationalism in the post-revolutionary period in the early 20th century —the only political consolidation period of Mexico—, Indigenous people often report themselves as mestizo and commonly forego their native heritage in favor of the national identity.