I remember 3 or 4 years ago when there was some day where all the Illegals were going to stay home and not work just to show the country how important Illegals were to the economy.
I remember on that day you could shoot a cannon ball down I-5 and not hit anyone. That made me a believer in building a fence so we could fix the traffic problem lol.
My guess is that there are many less Mexicans coming across the border to work in the construction trades then was the case last year and that is causing the decline in traffic.