Who are the biggest companies in the world? For years, this question has been answered by looking at a table of the market capitalisation of listed companies. That approach had one major flaw: it failed to take into account the vast amounts of corporate wealth hidden from equity markets.

State controlled, family-owned and private equity companies are an important driver of economic growth yet their “non-public” status makes it difficult to quantify their influence. The FT’s non-public 150, based on research from the management consultancy McKinsey, seeks to change that. By providing the first-ever ranking of unlisted companies, it sheds a revealing light over a fundamental, and fundamentally overlooked, part of the global capitalist system.