I've heard that physicists sometimes lose jobs with the economy and cut backs, and also that teachers are not in as much demand. If I have a degree in math, am I looking at slim pickings with jobs? I'm in the US.
You can't really make a true comparison.
As a teacher, you only work 163 days a year; you'll get tenure (they can't fire you no matter how terrible a teacher you are); the government will guarantee a fantastic retirement salary; and, if you choose to work (for there's nobody there to "look over your shoulder" on a daily basis), you'll only have to put in 5 - 45 minute teaching periods + 2 - 10 minute home room periods per day ( 245 minutes or 4 hours and 5 minutes). - Plus you can take out your frustrations on the kids.
As a Physicist you'll have to work at least 50 weeks a year and 40+ hours a week. So, based strictly on work hours, you'll have to make 124800/39935 ~ 3.125 times a teacher's salary to break even. - You'll have to be a "productive team-player" (which means you'll have to work hard and get along with everybody in the group) and you'll always worry about where your next contract will come from.
Oh, I forgot - As a teacher you'll get at least 5 personal days and 5 sick days (which, of course, you'll take) which means that you'll only have to work 153 days a year which means that you'll have to make ~ 3.3 times a teacher's salary - and there's always the perks of state paid for "teachers' conferences" and "field trips".
I pretty much agree with what the first person has said. There are some physicists who have what could be called high incomes, but it depends on what they do, and where they work. If they own their own business doing contract work, then there's a good chance they have a high income. All in all, the math teacher probably makes a higher income compared to most physicists, and has better job security after a few years of teaching.
Don't forget that being happy with the work you do is a part of happiness too. Income is not the only defining factor in being content with work.