What I have graphically mapped out below is probably a useful and efficient investment tool, especially for investors who are interested in diversification across industries.
Diversification mixes a wide variety of investments within a portfolio. A well-diversified portfolio consists a mix of distinct asset types, investment vehicles and even across industries to limit exposure to any single asset or risk.
In 1999, MSCI and S&P Dow Jones Indices developed the Global Industry Classification Standard (GICS) to capture the breadth, depth and evolution of industry sectors.
GICS is a four-tiered, hierarchical industry classification system.
Companies are classified quantitatively and qualitatively and assigned a single GICS classification at the Sub-Industry level according to its principal business activity. Revenues and market perception are key factors in determining a firm’s principal business activity.
I stopped at the Industries-level as it suffice for the average investors. Going too in depth will probably be too micro and not very useful for investment assessment.
Do you diversify across industries too?
Theory of Constraints 
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