It would be the 3rd derivative. Inflation is the first (rate of change of prices). The increase of Inflation is the second (rate of change of inflation). Therefore the decrease of the increase of inflation is the third

Oh that makes sense, inflation being first deriv is what I wasn’t catching. Thank you.

inflation = d price / dt

"rate of increase of inflation" (RII) = d inflation / dt

"decreasing rate of increase" = d RII / dt

Acceleration of inflation is the second derivative, the rate of change of that acceleration (what Nixon is referring to), is the third.

Yes, because inflation is already the first derivative of cost.

So the 'rate of increase' of inflation is the second derivative. And to say that the second derivative is decreasing is another way of saying the third derivative is negative

Third I think. First is the inflation rate itself (some positive number around 8%), second is how that rate is changing (some positive number meaning we expect the inflation rate itself to increase next interval) third is how that change itself is trending (negative I think? meaning that we'd expect the still overall positive increase to the base inflation rate to be somewhat less than it was in the previous interval).

Take that with a grain of salt, I'd welcome any corrections if some one sees fit.