,
A continuous function can only have one value for each tax rate (t). This is definitional.
Well, when you were taking economics I was getting a math degree at an Ivy League university, and that's not what the definition of continuous is...
The curve you have linked has multiple violations of this and is thus nonsensical.
No, the curve I linked connects all the actual, historical values of tax receipts versus marginal tax rate over the past few decades in the United States. (Other curves would too, of course.) The fact that it's nothing like a parabola is an inconvenience for those who would use Laffer's "curve" to interpret events or dictate policy...
