It all depends on what you want to do with the major. Salary will vary depending on the job you hold within the degree. For example, environmental health jobs will vary on salary and employment. You have to look at geographic location, what the job market is like where you reside or plan on residing after college. You also have to look at the different types of positions one could do with the environmental health degree.
The same goes for social work. I have a degree in social work and work in health care regulatory compliance. My salary is going to be different from someone working in a different job, perhaps as a mental health case-manager; or an adoptions specialist; or as a therapist; or as a child protective services worker; a juvenile officer; a probation and parole officer; a hospital social worker; a home health social worker; a hospice social worker; domestic violence social worker; victims advocate.......and the list goes on. Comparing one social work job is just that, comparing one social work job. The US Bureau of Labor Statistics 2010 Median salary for social workers: $42,480 per year/ $20.42 per hour. Of course it does not denote "degree" whether they used BSW and MSW to get those figures. http://www.bls.gov/ooh/Community-and-Social-Service/Social-workers.htm
For example, MSW level social workers who work for the federal government can have a salary range of 57,408 - $74,628 a year. http://www.indeed.com/jobs?q=vet+technician&l=#jk=d3c8b6bd887020c7
If planning on looking into working in health care organizations like hospitals or nursing homes, then one would definitely need to be a Registered Dietician, as a Nutritionist in most states has no certification requirements. That is why insurance pays for RD's, because RD's have set curriculum requirements and it is "standard". Some states, including mine, require RD's to be licensed with the State. According to the US Bureau of Labor Statistics Outlook Handbook, the 2010 Median income for RD's was $53,250 per year /$25.60 per hour. With Median, that does not mean "starting" salary.
Vet techinicians 2010 Median Salary: $29,710 per year
$14.28 per hour (from the below link at the US Bureau of Labor Statistics Outlook Handbook)
"Veterinary technologists and technicians must complete a postsecondary program in veterinary technology. Technologists need a 4-year bachelor’s degree, and technicians need a 2-year associate's degree. Typically, both technologists and technicians must take a credentialing exam and must become registered, licensed, or certified, depending on the state."
Again, the job market for vet techs will depend on the availability of positions where you reside. Just did a job search and one job for a vet tech requiring approximately three years experience had a salary range of $10 - $15 an hour. http://www.indeed.com/jobs?q=vet+technician&l=
Secondary Teaching salaries also vary, depending on whether you are teaching at public school.......which public school system, the state; or private schools. The Outlook Handbook for 2010 has the median salary as 53,230 per year for high school teachers. The job market again will vary on where you are looking for jobs. The job market is largely based on your geographic location. For example, in smaller communities where there are not that many schools......positions may not come open unless a teacher retires. Again, location location location.
But ultimately, I think what is most important is what we see ourselves doing in our life. We spend a lot of time and money on college....and it is an investment. It is important to really know what we can actually do with the degree and to figure out whether that it is a good career choice. We are all different in our personalities......some people like routine. Some people like to come to work not knowing what is going to happen. Some people like sitting in an office setting and working in front of a computer. While others want to be outside or working in an environment where they are not restricted to an office or cubicle.
As far as overall.........what is in demand? It depends on several factors: Location, location, location