The Size Group is a classification of a stock according to its relative Market Capitalisation, based on common heuristic cut offs for what constitutes a large or a small company. Any company with a Market Capitalisation of less than GBP 50 million is classified as a Micro Cap, less than GBP 350 million is a Small Cap, less than GBP 2.5 billion is a Mid Cap and all larger companies are Large Cap.
Many famous investors have made their fortunes, and their names, investing in small caps. Jim Slater, the famous British investor, once remarked that ‘Elephants don’t Gallop’. Smaller companies are less well researched, and have less analyst coverage than larger companies which often provide opportunities for dedicated investors.
There is much evidence amongst academic finance research papers that small caps on average outperform large caps over the long term, though in recent decades this has become disputed. Many new papers have shown that micro-caps, the very smallest companies, tend to be priced like ‘Lottery Tickets’ and have negative aggregate returns.
As small caps and large caps can outperform at different times, diversification across size groups is often highly recommended.