What's a lie that keeps coming back, no matter how often it's proven false?

We'll cut taxes but the economy will grow so much that we'll actually make more money. Even though the percentage the government gets will be lower the economic boom will be unparalleled, just trust me bro.

Whats a lie that keeps coming back, no matter how often its proven false?

I wanna hear your examples though :)

It doesn't have to be in politics or economics it can be in any area of life.

What's a lie that keeps coming back, no matter how often it's proven false?
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