The government blamed local police and drug cartels for the disappearance, and alleged that the students had been burned to ash in a massive pyre at the Cocula garbage dump in the state of Guerrero. But international experts have since concluded that this explanation, which was called the “historical truth” by Mexico’s attorney general, was scientifically impossible.

In August 2014, a month before Ayotzinapa, as the incident is known, Peña Nieto had an approval rating of 47%. By November, it dropped to 41%.

But these numbers don’t capture the full effect of Ayotzinapa on Peña Nieto’s popularity. Each revelation, and each apparent attempt to hide what happened, further eroded the public trust in the presidency.

It seems that any protest in the capital, no matter the subject, still includes signs that reference the events of Sep. 26. On Mexico City’s most famous boulevard, Paseo de la Reforma, a simple monument of a plus sign and the number 43 reminds pedestrians and motorists of the unanswered questions, and the thousands of other disappeared people throughout Mexico.