Credit

Almost 60 percent of the respondents to an Imagen poll say that official cooperation at the local, state, and federal level is responsible for the drop in violence, which is the government's explanation. 

Assigning credit and blame for the ups and downs in security is an extremely fraught exercise; the government could do everything right, but the violence could explode because of factors outside of its control. Likewise, the opposite could be true. I'm not saying either is the case, but the number of murders seems a crude measure of the government's performance. Nonetheless, it's odd that at least in terms of approval ratings, the public was slow to blame Calderón for the explosion of drug violence, yet when it drops slightly, he is the principal beneficiary.