...except we’re not discussing Mexican drug cartel violence, we were discussing the effect of a physical wall on illegal immigration.
I’m not even entirely sure what your graph is referencing or where it’s from. It’s not labeled or cited, except for years along the side and 8.122.
A quick googling of some key phrases reveals this: https://en.m.wikipedia.org/wiki/Timeline_of_the_Mexican_drug_war
...in which time we find out that in 2007, approx. 2500 people were killed due to drug violence, steadily climbing to over 15,000 killed in 2010.
But again, we’re not talking about drug violence. We’re talking about illegal immigration which won’t be stopped by a wall because most illegal immigrants aren’t walking across the border. They’re coming in shipping containers, in the backs of trailers, by plane.
https://www.pewresearch.org/fact-tank/2019/06/28/what-we-know-about-illegal-immigration-from-mexico/
https://www.pewresearch.org/fact-tank/2019/06/12/5-facts-about-illegal-immigration-in-the-u-s/
It also bears mentioning that while illegal immigration from Mexico has decreased since 2010, it’s increased from other South American countries in the last four years.
The wall hasn’t done a thing other than cost us a couple hundred billion in tax dollars and be used as a vehicle to bilk investors out of 25 million.
https://www.justice.gov/usao-sdny/press-release/file/1306611/download