When assessing stock portfolios, people mainly focus on the various GICS sectors and industries and which are overweight or underweight. We like to focus on classifying companies by risks and macroeconomic drivers, not based on what sector of the market they are classified in.
Diversification isn't just about the number of stocks in your portfolio. You can have many stocks all subject to the same risk factor. For example, here's a list of six stocks which all superficially appear to be different and span three sectors (industrial, technology, and consumer discretionary). But they all have