Why is it that to convert a Semi-Annual Modified Duration to an Annual one, we divide by 2 instead of multiplying by 2?
Surely it doesn’t imply that the bond price will move more in half a year than in one full year when interest rates shift?
1 year = 2 semi-annual periods. 
We were all Durs early on in our respective journeys!!! 
I can understand that, 2 semi-annual periods is equivalent to 1 annual period.
What’s bothering me a little bit is that makes sense in a duration/time basis.
The name Modified Duration itself implies it is a measure of time, length of duration, yet it measures a % price change in response to another variable unrelated to time.
Am I missing a point here? Does annual ModDur signify the %change in bond price with a 1% change in YTM over a course of 1 year? Is that what i’m missing?
The other variable is, in fact, related to time. Most finance people don’t understand that, and even finance professors miss it.
Yes.
Answer me this, if you please: What are the units on YTM?