Taxes are usually used to pay for social services, so if you were taxed 100% (a ludicrous notion since over time, you're tax income would reduce to zero, but let's roll with it), we assume that the government would pay for government housing, health care, food, etc. Plus, under slavery, you have no legal benefits because you are property.

Of course, that would never happen. 100% tax is not beneficial for you or the government:

http://upload.wikimedia.org/wikipedia/commons/thumb/3/36/Laffer-Curve.svg/745px-Laffer-Curve.svg.png