Is it objectively or subjectively better to be in the USA than in Mexico?
It isn't the climate , Mexican climate is not much different in the north of Mexico and never gets as severely cold as the north of the US.
It isn't the culture , Mexicans have to put up with what they must consider odd food , odd customs and a language barrier that they are expected to bridge .
It isn't family , for most of them there is more family back home waiting for the remittance.
When Mexico catches up and produces more jobs , there will be a direct effect on immigration . Mexicans who can achieve a reasonable income and standard of living close to their families, stores and restaurants that have familiar foods , clerks in all the offices that speak intelligibly etc... Will probably stay in Mexico in huge numbers.
So Ford Motor Company is doing more to effect reduction in illegal immigration this year than any US president has done for twenty years.
http://www.cnbc.com/2016/04/05/ford-adding-plants-jobs-in-mexico.html