Does "benefits" also include the tax contributions the company pays? After being 1099 for so long, those definitely sound like a benefit to me!
They technically call it 'fringe benefits'. My university has four categories of fringe benefits:
Full
Limited
Partial
Grad Health
The only things it specifies are that partial includes social security and full includes life insurance. But given that whatever I set for a post doc/research scientist/etc. salary is the amount they are paid, I assume that everything else including payroll taxes are encompassed in that 1/3 extra for fringe.