He doesn't even condone speeding. Neilson estimates that half of all taxpayers file completely accurate returns, with 10 percent inadvertently underpaying on income tax and 10 percent overpaying, again by mistake. If you look at other areas in which people cheat, such as speeding, you'd expect a lot more than that.
People speed a lot.
But people aren't cheating as much on taxes as they do in other situations. His research is the first use of Newcomb's problem in an economic setting. The person choosing must take only the opaque box or both boxes. But the offering entity, knowing the choice in advance, leaves the opaque box empty for those it knows will choose both boxes. In earlier behavioral studies using Newcomb's problem, participants split about 50-50 on which they would choose if faced with the situation.