I’m a high school senior applying to the UCLA & UCSD. I want to major in either econ or econ/math (preferably econ/math but I’m not sure if I can handle upper division math). Which major should I put as my primary and which as my alternate (is there one that is harder to switch into later). Also , can any UCLA/UCSD grads who majored in either of those tell me about their experience.
they are both really selective so, I would encourage you to apply to several schools (including some with high acceptance rates for your stats) and see what happens - only after you’ve been accepted do you need to narrow it down.
As far as major, put down the one you most want to study and let the chips fall where they may.
Apply broadly and good luck.
Thank you! Yeah, I know they are competitive 
- I was just wondering if anyone has recommendations on which to put down?
Both majors are in the College of Letters and Sciences for UCLA which does not admit by major so select the major you would prefer to study.
UCSD admits into the University first and then into the major. Both Math and Econ are capped majors so it is recommended if applying to a capped major, you select an alternate non-capped major. If you select both for 1st choice and alternate, there is always the possibility you will get into UCSD as Undeclared.
UCSD criteria to declare math or economics if you enter undeclared:
https://www.math.ucsd.edu/~handbook/undergraduate/cappedstatus/
https://economics.ucsd.edu/undergraduate-program/entry-to-the-majors.html
UCLA criteria to declare math or economics:
https://www.math.ucla.edu/ugrad/majors/math-major
http://www.math.ucla.edu/ugrad/majors/mathecon
https://economics.ucla.edu/undergraduate/current-students/majors-and-minors/economics-b-a/