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Equilibrium Growth, Inflation, and Bond Yields - Duke University's ...

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The aggregate resource constraint is<br />

where Πt ≡ Pt<br />

Pt−1<br />

is the gross inflation rate.<br />

Yt = Ct + St + It + φR<br />

2<br />

� Πt<br />

Πss<br />

Nominal <strong>Yields</strong> The price of a n-period nominal bond P (n)<br />

t<br />

where P (0)<br />

t<br />

P (n)<br />

t<br />

= Et<br />

�<br />

1<br />

Mt+1<br />

Πt+1<br />

�2 − 1 Yt<br />

P (n−1)<br />

�<br />

t+1<br />

can be written recursively as:<br />

= 1 <strong>and</strong> P (1)<br />

t = 1 . The yield-to-maturity on the n-period nominal bond is defined as:<br />

Rt+1<br />

2.2 Exogenous <strong>Growth</strong><br />

y (n)<br />

t<br />

≡ − 1<br />

n log<br />

�<br />

This setup also nests a fairly st<strong>and</strong>ard New Keynesian setup with exogenous growth when the technological<br />

appropriability parameter η is set to 0 <strong>and</strong> the aggregate stock of R&D Nt is exogenously specified. Under<br />

P (n)<br />

t<br />

these conditions the production function of the intermediate firm can be expressed as<br />

�<br />

Xi,t = K α i,t(ZtLi,t) 1−α<br />

Zt = AtNt<br />

where Nt follows a stochastic process. Note that TFP is now exogenous <strong>and</strong> comprised of a stationary<br />

component At <strong>and</strong> a trend component Nt. I consider two versions of the exogenous growth model, one with<br />

a deterministic trend <strong>and</strong> the other with a stochastic trend in productivity, to compare with the benchmark<br />

endogenous growth model.<br />

Deterministic Trend The law of motion for Nt is<br />

Nt = e µt<br />

where µ is parameter governing the average growth rate of the economy. Equivalently, this expression can<br />

be rewritten in log first differences as<br />

∆nt = µ<br />

12

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