<P> The Pareto principle or 80--20 rule is a 20th - century analogue . For example, it commonly takes 20% of the full time to complete 80% of a task, while to complete the last 20% of a task takes 80% of the effort . Achieving absolute perfection may be impossible and so, as increasing effort results in diminishing returns, further activity becomes increasingly inefficient . </P> <P> Robert Watson - Watt, who developed early warning radar in Britain to counter the rapid growth of the Luftwaffe, propounded a "cult of the imperfect", which he described as, "Give them the third best to go on with; the second best comes too late, the best never comes ." </P>

Do not make perfect the enemy of good