It Is Better To Be Roughly

This maxim is widely attributed to Keynes, though its precise source is debated — it does not appear verbatim in his major works. It is consistent with his pragmatic, anti-perfectionist approach to policy and forecasting: Keynes repeatedly argued against waiting for certainty before acting, and The General Theory (1936) was itself full of deliberately approximate models. The phrase has become a standard rejoinder in economics and statistics against over-precise models built on faulty assumptions.