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investment by a corresponding y0j θjh, at date 0, and θjh entitles h to receive
ysj θjh in state s (for all s in S), at date 1.
At time zero, consumers can also trade in bonds, which are assets in zero
net supply. The (after-tax) asset matrix is W = (W1, W2), where
W1= ... (1 +qtjs1)Rsj j∈J1
(N×J1)
W2 =
y0j - qj
Mj (y1,t1)
j∈J2
(N×J2)
and Mj(y 1, 11 ) has typical s-element mj = ( 1+ts1 )yj .Lastly, agents face the
same financial structure W. Thus, they all have equal access opportunities
to the equity market. Bankruptcy or default is not allowed.
2.1.4. The consumer problem
For notational simplicity, let
eh = I ehh + ∑qjθ^,eh + t10
j∈J2
define the total after-tax endowment of a typical consumer h. The individual
budget set, for given financial opportunities W and total endowments eh, is
B w eh ) = Ph ∈ R +:Xh ≥ eh= ∈Jφ
An individual optimum for h, at (W,eh), is a pair (xh, ^θ)h) such that xft
maximizes uh(xh) on B W ∙eh), and ^θh satisfies xh — eh = Wθh, and
θjh ≥ 0forallj inJ2.
At an interior individual optimum, xh' ^ 0, the present value vector (or
stateprice) of consumer h instate s isλh = λh(xh) = Dxsu(xh)∕Dx0 0 u(xh).
Let ( W) denote the column span of W, a subspace of dimension (at most)
equal to J. Its orthogonal complement, ( W) ⊥, has (at least) dimension N — J.
If we assume, for the moment, that the no-short sale constraints are non-
binding, λh ∈ (W)⊥.
2.1.5. The firm’s problem If we keep on abstracting from the no-short sale
constraints, the fact that, at the individual optimum, present value vectors
satisfy λh ∈ (W)⊥, implies that consumers do not typically agree on the
evaluation of future income profiles. Since consumers are also firms’ share-
holders, the latter poses problems for the definition of the objective function
of the firm. Precisely, if the firm chooses its production plans in the best