Econometric Models for Count Data with an Application to the Patents-R&D Relationship
Bronwyn Hall and
No 17, NBER Technical Working Papers from National Bureau of Economic Research, Inc
This paper focuses on developing and adapting statistical models of counts (non-negative integers) in the context of panel data and using them to analyze the relationship between patents and R&D expenditures. The model used is an application and generalization of the Poisson distribution to allow for independent variables; persistent individual (fixed or random) effects, and "noise" or randomness in the Poisson probability function. We apply our models to a data set previously analyzed by Pakes and Griliches using observations on 128 firms for seven years, 1968-74. Our statistical results indicate clearly that to rationalize the data, we need both a disturbance in the conditional within dimension and a different one, with a different variance, in the marginal (between) dimension. Adding firm specific variables, log book value and a scientific industry dummy, removes most of the positive correlation between the individual firm propensity to patent and its R&D intensity. The other new finding is that there is an interactive negative trend in the patents - R&D relationship, that is, firms are getting less patents from their more recent R&D investments, implying a decline in the "effectiveness" or productivity of R&D.
References: Add references at CitEc
Citations: View citations in EconPapers (1154) Track citations by RSS feed
Published as Hausman, Jerry A., Bronwyn Hall, and Zvi Griliches. "Econometric Models for Count Data with an Application to the Patents-R&D Relationship." Econometrica, Vol. 52, No. 4, pp.909-938, July 1984.
Downloads: (external link)
Journal Article: Econometric Models for Count Data with an Application to the Patents-R&D Relationship (1984)
This item may be available elsewhere in EconPapers: Search for items with the same title.
Export reference: BibTeX
RIS (EndNote, ProCite, RefMan)
Persistent link: https://EconPapers.repec.org/RePEc:nbr:nberte:0017
Ordering information: This working paper can be ordered from
Access Statistics for this paper
More papers in NBER Technical Working Papers from National Bureau of Economic Research, Inc National Bureau of Economic Research, 1050 Massachusetts Avenue Cambridge, MA 02138, U.S.A.. Contact information at EDIRC.
Bibliographic data for series maintained by ().