The consideration in welfare economics of when it is a good thing to satisfy ‘optimum conditions’. Economists can draw up sets of necessary and sufficient conditions for the efficient operation of an economy. If all but one of these conditions were already satisfied, it would always be beneficial to satisfy the remaining condition: this would give rise to a first-best situation. If, however, some of the necessary and sufficient conditions cannot be satisfied for any reason, then it may or may not be beneficial to satisfy any particular condition: this requires investigation case by case. A second-best optimum is one where the best decisions are made about whether or not to satisfy some optimum conditions when others cannot be satisfied.

• nominal anchor
• nominal protection
• nominal variable
• nominee holding
• non-accelerating inflation rate of unemployment
• non-contributory pension scheme
• non-discrimination
• non-durables, consumer
• non-executive director
• non-inflationary growth
• non-intersecting curves
• non-linear function
• non-marketable debt
• non-marketed economic activities
• non-monetary job characteristics
• non-negative
• non-parametric statistics
• non-performing debt
• non-positive
• non-price competition
• non-satiation
• non-systematic risk
• non-tariff barriers
• non-tradables
• non-voting share