“…9 The (often misconstrued) "shrinkage" method[Ledoit and Wolf, 2004] is nothing but a special type of statistical risk models; see[Kakushadze, 2016],[Kakushadze and Yu, 2017] for details. 10 E.g., BICS (Bloomberg Industry Classification System), GICS (Global Industry Classification Standard), ICB (Industry Classification Benchmark), SIC (Standard Industrial Classification), etc.11 The number of relevant style factors is even fewer in short-horizon risk models for use, e.g., in short-horizon quant trading applications[Kakushadze, 2015a], where it is 4 (or even fewer). 12 More precisely, this holds in the regression of 𝛹 𝛼 over 𝑥 𝛼 , demeaned 𝑦 𝛼 , and demeaned 𝑧 𝛼 .…”