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In page Free-rider problem:

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A free rider may enjoy a non-excludable and non-rivalrous good such as a government-provided road system without contributing to paying for it. Another example is if a coastal town builds a lighthouse, ships from many regions and countries will benefit from it, even though they are not contributing to its costs, and are thus "free riding" on the navigation aid. A third example of non-excludable and non-rivalrous consumption would be a crowd watching fireworks. The number of viewers, whether they paid for the entertainment or not, does not diminish the fireworks as a resource. In each of these examples, the cost of excluding non-payers would be prohibitive, while the collective consumption of the resource does not decrease how much is available.[citation needed]