Seems one is much more dependent than the other. What's strange to me is why people would do their shopping north of the border when, most of the same stores are in Mexico.
Hope you're not waiting on your MIL like me. MERRY CHRISTMAS
There are segments of the retail trade that don't exist on the mexican side.
Also better selection. Better quality. Better price.
There is also a cultural aspect to it in that it deals with class and conspicuous consumption. Those that can afford it will even go beyond the border area to San Diego, Tucson, or San Antonio.