Two indicators readily derivable from 1995 SDR data may be used to illuminate the relationship between the productivity of doctoral scientists and engineers and their age. The 1995 SDR collected information on two research outputs that may be used as a proxy to measure the productivity of doctoral scientists and engineers, namely publications and patents. The indicators examined in this report are the article publication rate and the patent activity rate.
The article publication rate (APR) is defined as the percentage of doctoral scientists and engineers in a given age group who authored or co-authored at least one paper accepted for publication in a refereed journal between April 1990 and April 1995. For employed doctoral scientists and engineers, the APR had progressively lower values for older age groups (table 8). For example, the APR of doctoral scientists and engineers aged 60-75 was only 40 percent as large as the value for the group aged 35-44. If only those employed doctoral scientists and engineers who were in the education sector are considered, the fall-off was more gradual: the APR for those aged 60-75 was 70 percent of that for the group aged 35-44.
Previous analysis has indicated that doctoral scientists and engineers in the education sector who published less frequently than their peers were more likely to leave full-time employment. For doctoral scientists and engineers aged 51-65, those who did not publish at all left full-time academic employment at four-year institutions between 1995 and 1997 at a rate more than twice that for those publishing six or more articles.
The patent activity rate (PAR) is defined as the percentage of doctoral scientists and engineers in a given age group named as an inventor on at least one U.S. patent application from April 1990 to April 1995. For employed doctoral scientists and engineers, the PAR also had lower values for older age groups but the decline in values was somewhat more gradual than for the article publication rate. For doctoral scientists and engineers aged 60-75, the PAR was about half (47 percent) that of the group aged 35-44 and about two-thirds (67 percent) of that for the group aged 45-59.
If only employed doctoral scientists and engineers in the education sector are considered, the patent activity rate for those aged 65-75 was about the same as for all doctoral scientists and engineers in education (7 percent versus 6 percent, respectively). In contrast, the article publication rate for those aged 65-75 (61 percent) was smaller than for all age groups combined (78 percent). Thus, there is some indication that, unlike publications, patent output within academe may not decline with age.
 Source: National Science Board, Science and Engineering Indicators: 2000 (Arlington, VA: National Science Foundation, NSB-00-1, 2000), pp. 3-24.
 Additional information in the 1995 SDR is available on numbers of patents granted as well as numbers commercialized. However, these variables, which require more elaborate analysis, were not examined for this report. Further information on how the number of patents granted and the number commercialized may be utilized as productivity indicators can be found in R. P. Morgan, C. Kruytbosch and N. Kannankutty, "Patenting and Invention Activity of U.S. Scientists and Engineers in the Academic Sector: Comparisons with Industry," Journal of Technology Transfer 26 (2001): pp. 173-83.
 For more detailed analysis, using SESTAT data, of the patenting and invention activity of U.S. scientists and engineers, see R.P. Morgan, C. Kruytbosch and N. Kannankutty, note 19.