that the number of firms in the market may not be the "ideal" one. That is,
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may be too much or too little entry. One way to think about this problem is in
terms of the externalities associated with entry. Whenever a new firm considers en-
tering the market with a new product,
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Yet its entry would also have two external effects:
384 PA R T F I V E F I R M B E H AV I O R A N D T H E O R G A N I Z AT I O N O F I N D U S T R Y
N The product-variety externality: Because consumers get some consumer surplus
from the introduction of a new product,
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positive externality on consumers.
N The business-stealing externality: Because other firms lose customers and