TY  - JOUR
AU  - Pindyck,Robert S.
AU  - Rotemberg,Julio J.
TI  - Do Stock Prices Move Together Too Much?
JF  - National Bureau of Economic Research Working Paper Series
VL  - No. 3324
PY  - 1990
Y2  - April 1990
UR  - http://www.nber.org/papers/w3324
L1  - http://www.nber.org/papers/w3324.pdf
N1  - Author contact info:
Robert S. Pindyck
MIT Sloan School of Management
100 Main Street, E62-522
Cambridge, MA  02142
Tel: 617/253-6641
Fax: 617/258-6855
E-Mail: RPINDYCK@MIT.EDU

Julio J. Rotemberg
Graduate School of Business
Harvard University, Morgan Hall
Soldiers Field
Boston, MA  02163
Tel: 617/495-1015
Fax: 617/496-5994
E-Mail: jrotemberg@hbs.edu
AB  - We show that comovements of individual stock prices cannot be justified by economic fundamentals. This finding is a rejection of the present value model of security valuation. Unlike other tests of this model, ours is robust in that it allows for volatility in ex ante rates of return. The only constraint we impose is that investors' utilities are functions of a single consumption index. This implies that changes in discount rates must be related to changes in macroeconomic variables, and hence stock prices of companies in unrelated lines of business should move together only in response to changes in current or expected future macroeconomic conditions. We also show that this constraint implies that any priced factors in the APT model must be related to macroeconomic variables. Hence our results are also a rejection of the APT, so constrained.
ER  -