OK, that matches what I was thinking. The trick is that to make it equivalent to basic income, the threshold level you describe would be different from the equivalent basic income level.
For example, if you take a basic income system with a $20k guaranteed minimum income - if you tried to recreate that with a negative tax bracket and a threshold of $20k, you would need to pay 100% of the shortfall. And even then, you would effectively have a 100% marginal tax rate; until you make $20k there is no financial incentive to work at all.
Instead, to get the equivalent of a $20k GBI, you would need to do something like, set a $40k threshold, with a negative tax of 50% of your shortfall. So at 0 income you get $20k. (And at 10k income you get 15k in negative tax, for a total of 25k, etc.) Of course, your marginal tax in that example is still very high at 50%. To make the marginal tax rate low, which is desirable at low income levels, you would either need to set a very high threshold, or more likely, have multiple negative tax brackets at different rates.
What I still fail to see is how this is "better" than a standard guaranteed income. It just seems like people will find it much more confusing than providing a fixed amount to everyone and having positive tax brackets as we do already (albeit different ones).
For example, if you take a basic income system with a $20k guaranteed minimum income - if you tried to recreate that with a negative tax bracket and a threshold of $20k, you would need to pay 100% of the shortfall. And even then, you would effectively have a 100% marginal tax rate; until you make $20k there is no financial incentive to work at all.
Instead, to get the equivalent of a $20k GBI, you would need to do something like, set a $40k threshold, with a negative tax of 50% of your shortfall. So at 0 income you get $20k. (And at 10k income you get 15k in negative tax, for a total of 25k, etc.) Of course, your marginal tax in that example is still very high at 50%. To make the marginal tax rate low, which is desirable at low income levels, you would either need to set a very high threshold, or more likely, have multiple negative tax brackets at different rates.
What I still fail to see is how this is "better" than a standard guaranteed income. It just seems like people will find it much more confusing than providing a fixed amount to everyone and having positive tax brackets as we do already (albeit different ones).