I think it's been quadratic with a pretty low contribution from the order 2 term.
Think of the number of events that can flip a bit. If you make bits smaller, you get a modestly larger number of events in a given area capable of flipping a bit, spread across a larger number of bits in that area.
That is, it's flip event rate * memory die area, not flip event rate * number of memory bits.
In recent generations, I understand it's even been a bit paradoxical-- smaller geometries mean less of the die is actual memory bits, so you can actually end up with fewer flips from shrinking geometries.
And sure, your other effect is true: there's a whole lot fewer bitflips that "matter". Flip a bit in some framebuffer used in compositing somewhere-- and that's a lot of my memory-- and I don't care.
Think of the number of events that can flip a bit. If you make bits smaller, you get a modestly larger number of events in a given area capable of flipping a bit, spread across a larger number of bits in that area.
That is, it's flip event rate * memory die area, not flip event rate * number of memory bits.
In recent generations, I understand it's even been a bit paradoxical-- smaller geometries mean less of the die is actual memory bits, so you can actually end up with fewer flips from shrinking geometries.
And sure, your other effect is true: there's a whole lot fewer bitflips that "matter". Flip a bit in some framebuffer used in compositing somewhere-- and that's a lot of my memory-- and I don't care.