There's really no need for you to draw any inferences from my posts regarding my position. I thought I had made it absolutely clear, on more than one occasion, where I stood on this debate.
For the avoidance of any doubt, I am essentially in favour of maintaining the status quo regarding our current inheritance tax regime.
I am certainly trying to test the strength of your arguments but that doesn't necessarily mean that I'm in favour of increased inheritance taxes. It seems to me that the logic of your arguments would suggest that we should repeal inheritance taxes completely, which I would consider a regressive step.
As it happens, I have read "Our Kids" but I don't recall any argument being made by Robert Putnam to the effect that inheritances are not a major cause of wealth inequality in the US. If you could point me to the relevant passages or indeed to any other data that supports your position in this regard that would be greatly appreciated.
I certainly don't agree that taxes on income or gains have the same impact on productivity as inheritance taxes. I simply don't believe that an individual's behaviour is very strongly influenced by the possible taxation of their estate whereas it seems obvious to me that high rates of income tax have a significant influence on individual behaviour. I would suggest that Robert Putnam would appear to support the later position as he has advocated increasing income tax credits on earned income.
Income tax certainly accounts for a far higher proportion of the State's revenue than inheritance taxes but I don't see what that has to do with the principle as to whether or not it is appropriate to tax inheritances in the first place and, if so, at what level.