A City Guide To Husainpur for perfect competition: an industry that consists of many small firms who, as individual firms, are unable to influence the market price. Perfectly competitive firms produce identical products (standardized goods) and operate in industries where the barriers to entry or exit are nonexistent. per unit tax: a tax levied on the sale of a good, where each unit sold is taxed at the same rate (e.g., an excise tax). Phillips Curve: an observed (graphical) relationship between unemployment rates and the rate of inflation. Economists often debate as to the nature of this relationship, in terms of whether the relationship is negative, positive, or even possibly nonexistent. A City Guide To Husainpur 2016.