I think a wealth tax is a good idea. Yes, the level would have to be set carefully, but as for most people that probably means 'as long as it's set a bit above my own circumstances', I'm not sure that it would ever be a vote winner
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I think it has to be far enough above average that it doesn't penalise ambition and it shouldn't be possible to opt out. I'm not sure what average wealth is, but maybe a tax should start at something like three times whatever it is, including investments, property, savings and pensions, and go up from there?
I wouldn't weight it to account for geographical house price differentials, as not doing so might contribute to the 'levelling up' that keeps being promised to areas outside of London and the SE. It should, probably, be weighted to take account of age, however, as older people are sure to (and need to) have more in savings and pensions than the young, and less (if any) ability to earn more.
It would be great if the Welfare bill could be cut, but the only way to do that would be to have strict rent controls, a realistic minimum wage and free, or heavily subsidised childcare. With those in place, people could be expected to support their families through work, and could do so with dignity.
If they are capable of work but then choose not to, that's up to them, but there is, IMO, no need for the rest of us to have to do so if everyone can afford to pay for housing and childcare. As things are, there is little incentive, as wages are so low, rents are so high and childcare so expensive that people can be better off on benefits than working.