Real world market structures (especially oligopoly and monopolistic competition), all of which fall short of the idealized characteristics of perfect competition, can then be compared against the perfectly competitive benchmark. The fun part of economic analysis is then to see how and where particular industries fall short and the degree to which each of these specific characteristics contribute to the lack of efficiency.

Consider Phil the zucchini grower. As one of gadzillions of zucchini growers, each producing identical zucchinis, Phil would seem to be operating in a perfectly competitive industry. But is he... really?

• First, consider the large number of growers characteristic. While there are gadzillions of zucchini growers, Phil does not compete with every zucchini grower in the nation. Because zucchinis are perishable and costly to transport, Phil's market is likely confined to his hometown of Shady Valley. In this case, he might be one of only a few hundred zucchini producers. Being one of a few hundred provides significantly more market control that being one of gadzillions.
• Second, consider the identical product characteristic. If Phil provides "service with a smile" and offers only the plumpest, juiciest, ripest zucchinis for sale, then buyers might prefer to buy Phil's zucchinis over those of other zucchini growers. In the view of the buyers, Phil's zucchinis are not identical to the other zucchinis in the Shady Valley zucchini market.
• Third, consider the perfect resource mobility characteristic. While Phil can easily exit the Shady Valley zucchini market by not planting any more zucchinis, there are barriers to entering the market. In particular, a zucchini grower needs a chunk of land upon which to grow zucchinis. While most homeowners in Shady Valley could easily clear a plot by the back fence, landless apartment dwellers or the homeless lack this opportunity. The cost of entering the zucchini market might be low, but it is not zero.
• Fourth, consider the perfect knowledge characteristic. A lot of folks are completely clueless when it comes to growing zucchinis. Are the seeds planted by a full moon in March? How far apart are the seeds planted? Do zucchinis grow on trees? Is it necessary to irrigate? How much and what kind of fertilizer is added? Are zucchinis harvested (or picked) when they are green, or yellow, or some other color? Moreover, what is the going price of zucchinis? Is it really $2.50? So many questions, so few answers. And certainly not perfect knowledge.