Facility size is also a factor. In both 1999 and 2000, hospital salaries increased with hospital bed size. Many nurses report that they're not compensated by their facility for specialty certification. If you have special knowledge and abilities, you can negotiate your salary. Compensation is also an issue with nursing education levels.
Some nurses report that they receive the same pay no matter what nursing degree they have.
With an MSN, I make the same as a diploma nurse. Another common lament is that nursing salaries don't rise in proportion to years of experience. My salary doesn't reflect my experience. Bad for me. A comparison of reported salaries in 1999 and 2000 shows that this may be changing.