ECO380H1 Lecture Notes - Lecture 3: Subgame, Root Mean Square, Production Function
ECO380: Tutorial Problem Set - For Wednesday, March 21, 2018
1. [Dixit] So far, we have worked through the idea of NE in the second part of the Dixit game - T=2,
once ¯
K1has already been chosen and rms are making their nal output decisions (and F2 is deciding
whether or not to enter, or set q2= 0 and avoid the xed costs F2). The production function is
qi= min{Li, Ki}- producing one unit of output requires one unit of labor and one unit of capital.
The demand for the rms' output is given by P= 50 −0.01Q. The wage rate is w= 10, and the rental
rate of capital is r= 10.
(a) Solve for F2's BR function.
(b) We know that if F2 decides to produce output, then the equilibrium of this subgame will be at
some point on F2's BR function. (It will also be on F1's BR function, but we don't know what
that is until we know ¯
K1!) Given that knowledge, solve for Π2(q1)- Firm 2's prots, as a function
of Firm 1's quantity (assuming F2 produces the prot-maximizing quantity of output, larger than
0).
(c) Solve for the two parts that we use to describe F1's BR function - their BR function when their
MC=w, and their BR function when their MC=w+r.
(d) What is the range of potential equilibrium quantities of q1that we could possibly have? (If you
get stuck, look at the graphs from the slides - there's a limit to how low or how high q1could be
in equilibrium, regardless of where ¯
K1is.)
(e) Given that range, what is the corresponding range of (before xed costs) prots to Firm 2?
2. [Dixit] In the Dixit model we saw in class, we discussed two benchmark values of ¯
K1,which we referred
to as M1and V1. Assume the same production function for output (one unit of output requires one
unit of capital and one unit of labor), for generic demand P=A−BQ , wage rate w, and rental rate
of capital r.
For some choices of these parameters A, B, w, r there is no possibility for predatory behavior: de-
pending on the value of F2Firm 2 either does not enter following monopoly behavior, or cannot be
prevented from entering. Only some combination of parameters A, B, w, r will make it possible that
there are some values of F2for which it is possible to prevent entry in a predatory manner (not by
acting like a monopolist).
What condition on A, B,w, and rmust be true for it to be possible for Firm 1 to prevent Firm 2 from
enterering for some values of F2? Here you are looking for an equation that these parameters must
satisfy if there are going to be any values of F2for which predatory behavior is possible. How does
this condition change if we instead needed two units of capital and one unit of labor to produce one
unit of output?
(To get you started: remember that the only time that behavior is predatory is when Firm 1 chooses
some ¯
K1∈(M1, V1]. So, they can only do something predatory if that interval is nonempty!)
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Document Summary
R t r s t t s p = 50 0. 01q r t s w = 10 t r t r t t s r = 10 . T st t t r s r t s s t r s t t r q1 . T t r t s t rr s r r sts r ts t r . T t t r r r p = a bq r t w r t r t . R s s t s r t rs a, b, w, r t r s ss t r r t r r . R t r t r s t r t rs a, b, w, r t ss t t t r r s s f2 r t s possible t r t tr r t r r t .