It would be better based on 86, the date of the last blanket amnesty. That would truly be the no diff between calculated and actual basis.
The big bump occurred, not due to 86 amnesty, but due to Clinton Treas Sec Rubin destroying the Mexican economy (for their own good) in the 90s. Rubin forced the Maquiladoras to flee Mexico for Asia. Those unemployed then looked for jobs where they could find them... here. When the fled there were no longer customers for the retail sector... So the retail employees...and business owners also came here.