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Uncertainty and Risk - DARP

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Microeconomics<br />

where the last term vanishes because of the …rst order condition. So<br />

@Eu <br />

@<br />

has the sign of E(u [p p]): But this must be positive if u is<br />

decreasing with <strong>and</strong> will be zero if u is constant. Hence the …rm strictly<br />

prefers certainty if it is risk averse <strong>and</strong> is indi¤erent between certainty <strong>and</strong><br />

uncertainty if it is risk neutral.<br />

2. For any known realization p we may write q = S(p) where S is the competitive<br />

…rm supply curve. Pro…ts as a function of P may thus be written:<br />

(p) = pS(p)<br />

C(S(p))<br />

which implies<br />

d(p)<br />

dp<br />

= [p C q ]S p (p) + S(p) = S(p) (8.20)<br />

where S p (p) is the slope of the supply curve at p, a positive number.<br />

Therefore, di¤erentiating (8.20) we have<br />

d 2 (p)<br />

dp 2 = S p (p) > 0:<br />

Hence () is increasing <strong>and</strong> convex. So it is immediate that E(p) > (p):<br />

cFrank Cowell 2006 133

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