I read in Schweser book 3, page 162:" A stock-based enhanced indexing strategy can produce higher information ratios because the investor can systematically apply her knowledge to a large number of securities, each of which would have different attributes requiring independent decisions"
I don’t understand thier explanation at all.
Yes, agree with you about exact and approximate fomula of calculating IR.
So the information ratio as its defined here by CPK is approximately equal to the other information ratio equation: Actice Return / Tracking Error, correct ? So really just another way of calculating IR?
The 2nd formula is known as Fundamental Law of active management. However, the breadth is not very well-defined.
It has been discussed as number of independent investment decisions not just the size of research universe.
I would imagine that a typical derivative based trategy use much less FI instruments to generate alpha than the number of stocks tilting required in a stock-based strategy. At least, that’s what CFA is saying.
But how the dependent/independent distinction comes into play here?
It has also been shown that the original Grinold IR formula tends to overestimate the realised IR and thus has to be adjusted downward.