Determining the population of scientists and engineers in the U.S. can be dramatically affected by the criteria used to define this group. Educational degree levels and fields, occupational categories, or a combination of these factors may all be taken into account. To better define and understand this population, the National Science Foundation (NSF) developed the Scientists and Engineers Statistical Data System, or SESTAT ('SEE-stat').
SESTAT was designed in response to recommendations of the National Research Council's Committee on National Statistics (CNSTAT). The committee, with support from NSF, was asked in the late 1980s to conduct a comprehensive review of the NSF's surveys and data on scientists and engineers and to propose methods and procedures for increasing the quality and usefulness of the data in the 1990s. As NSF was expecting to draw a new sample of experienced scientists and engineers from the 1990 decennial census, the opportunity was provided to examine the design and operation of NSF's S&E data system. The committee's analyses and recommendations for the data system were presented in their 1989 report Surveying the Nation's Scientists and Engineers: A Data System for the 1990s. As one of its principal proposals, CNSTAT stated:
"We strongly urge that the NSF personnel data system for the 1990s strive to provide information that will permit users to apply their own definitions of the science and engineering population to suit their particular research and analysis purposes within a framework that facilitates cross-comparisons with other widely used data sources. Specifically, we believe that the system should support analysis of the science and engineering community from each of two major perspectives... from the perspective of occupational employment or jobs and from the perspective of academic training or careers."
The NSF has strongly endorsed this recommendation and it has served as the guiding principle in the design and development of SESTAT.
SESTAT is a comprehensive and integrated system of information about the employment, educational, and demographic characteristics of scientists and engineers in the United States. It comprises data collected through three national sample surveys supported by NSF: the National Survey of College Graduates (NSCG), the National Survey of Recent College Graduates (NSRCG), and the Survey of Doctorate Recipients (SDR). These surveys are conducted biennially; each is administered to a different sample population of bachelor's and above college degree holders. Although there are individuals in the U.S. who have earned science and engineering related degrees at the associate's degree level or who do not have bachelor's degrees but are working in science and engineering occupations, these individuals are not included in the sampling frames for the three SESTAT surveys.
The National Survey of College Graduates
The NSCG was first administered in 1993 and biennially thereafter to a nationally representative sample of all college degree holders who were identified through the 1990 decennial census. The target population for this survey includes individuals in the United States as of April 1990 with a bachelor's degree or higher in any field, not just the sciences or engineering. Besides capturing people with degrees earned at U.S. institutions, the NSCG also includes college degree holders who earned their degrees outside of the United States but who were residing here in 1990. In 1993, two selected groups from the NSCG were incorporated into the SESTAT database: those with science or engineering degrees, and those without such degrees but working in S&E occupations. These two populations are collectively referred to as the NSCG S&E panel. In 1995 and subsequent rounds of the survey, these same two groups were followed.
The National Survey of Recent College Graduates
A second survey, the NSRCG -- which has been administered biennially since the early 1970s to recent S&E bachelor's and master's degree recipients -- is used to incorporate new U.S. S&E degree earners in the 1990s. In 1993, the NSRCG consisted of a sample of individuals who earned new S&E bachelor's and master's degrees in the 1990, 1991, and 1992 academic years. In 1995, these 1993 sample cases were moved into the NSCG sample frame; the 1995 NSRCG includes only recent U.S. S&E bachelor's and master's degree earners from the 1993 and 1994 academic years. The 1995 NSRCG sample was passed to the NSCG for the 1997 survey round; the 1997 NSRCG includes new U.S. S&E bachelor's and master's degree earners from the 1995 and 1996 academic years.
The Survey of Doctorate Recipients
A third survey, the Survey of Doctorate Recipients, has been sponsored by the National Science Foundation and other federal agencies since the early 1970s. In this survey, a sample of holders of S&E doctorates earned at U.S. institutions are followed throughout their careers from year of degree award until age 75. Every 2 years, a sample of new S&E doctoral degree earners is added to the SDR from another NSF-sponsored survey, the Survey of Earned Doctorates. In 1993, the SDR sample frame included all U.S.-earned S&E doctorates through academic year 1992; the 1995 sample frame includes doctorates earned through the 1994 academic year; the 1997 sample frame includes doctorates earned through the 1996 academic year.
The SESTAT Integrated Database
The SESTAT database was created by the integration of the S&E Panel of the NSCG, the NSRCG, and the SDR. Table 1 is a summary of the populations included in these three component surveys of the SESTAT integrated database. Because after 1993 the SESTAT surveys identify individuals for inclusion only at the point of earning a new S&E degree from a U.S. institution, two subpopulations of scientists and engineers in the United States are underrepresented in the SESTAT integrated database in 1995 and subsequent survey years: (1) new immigrants with S&E degrees earned outside the U.S. who entered the U.S. after 1990, and (2) people with no S&E degrees working in S&E occupations after 1990.
The SESTAT integrated database captures that part of the science and engineering population who either received a college degree (bachelor's or higher) in an S&E field or those who work in an S&E occupation with a bachelor's degree or higher in any field. This is a broad designation that includes many fields of study, as well as many occupations. The dashed oval on Figure 1 shows the groups of individuals included in the SESTAT integrated database. There are other groups in the U.S. population that can be considered part of the population of scientists and engineers, for example persons in technical occupations without college degrees, who are not included in the SESTAT integrated database. The SESTAT system was developed to provide information on the bachelor's and above population of scientists and engineers, with emphasis placed on those trained at U.S. institutions.
The 1993 SESTAT integrated database represents 11,615,200 individuals. This included 11,021,500 persons with S&E degrees, and 593,600 persons without such degrees but working in S&E occupations (table 2).
The 1995 SESTAT integrated database represents 12,036,200 individuals: 11,456,600 with S&E degrees; 334,100 persons without such degrees but working in S&E occupations, and 245,400 persons without S&E degrees or jobs.
Approximately 84 percent of the individuals in the 1993 and 1995 SESTAT integrated databases (9,793,500 and 10,114,500, respectively) were employed. Among this group, about one-third were employed in science or engineering occupations (3,303,400 in 1993 and 3,185,600 in 1995). Individuals in this group are often referred to as those working in S&E. The remaining individuals were either unemployed, but seeking work (322,200 in 1993 and 249,300 in 1995) or were not in the labor force (1,499,500 in 1993 and 1,672,400 in 1995).
Many of the individuals in the 1993 and 1995 integrated databases hold either multiple S&E degrees or have degrees in both S&E and non-S&E fields. There were 11,021,500 individuals in 1993 who were educated in S&E; that number had risen to 11,456,600 by 1995. Approximately three-fourths of these individuals reported that their highest degree was in an S&E field (8,571,000 in 1993 and 8,908,000 in 1995).
Many workers educated in S&E routinely find occupations in non-S&E fields. Roughly 70% of all S&E-educated individuals in the labor force were employed in non-S&E occupations (6,490,100 in 1993 and 6,718,600 in 1995). Conversely, but to a lesser extent, non-S&E educated individuals are employed in S&E occupations. In 1993, there were 593,600 non-S&E educated persons working in S&E occupations. In 1995, the SESTAT integrated database included only 334,100 persons in this category.
There is a wide range of information on scientists and engineers contained in SESTAT. Listed here are examples of the variables found in the SESTAT integrated database.
Labor Force Information
For the employed:
For the unemployed and those not in the labor force:
Other Work-Related Information
1993: Labor force status in 1988
1995 (SDR only): Post-doctoral experience
1995 (NSCG and SDR only): Patent and publication activity
1997: Alternative or temporary work experience
SESTAT is useful not only for describing the characteristics of the U.S. scientists and engineers, but also for answering questions about this group. For example, it can be used to describe the educational background of engineers or social scientists. Analysts can use the system to show what occupations people with physics degrees hold. It can also be used to answer questions such as how age or gender are related to salary distributions for scientists or engineers working in different fields or with different degrees. SESTAT is intended to support this type of research, for both policy analysis and general information.
The Division of Science Resources Studies has produced a variety of analyses that show the capability of SESTAT for analyzing characteristics and issues about the U.S. population of scientists and engineers, including the following examples:
The concepts used to develop the SESTAT integrated database are broad and general in order to provide the capability for flexible and customized analyses. As such, SESTAT users may tailor their inquiries and research to address a variety of issues about the population of scientists and engineers.
The SESTAT system is available to the public on the World Wide Web at http://sestat.nsf.gov. This site contains public use versions of the SESTAT integrated databases for 1993 and 1995, as well as a public use version of the 1993 NSCG database. The 1997 integrated database will be available in Spring 1999. The National Science Foundation ensures the confidentiality of all of the data collected and available in the SESTAT system.
 For 1993, the full NSCG file (which includes all college degree holders, both S&E and non-S&E) is available for analysis. This file can be obtained on CD-ROM, or accessed through the SESTAT web site.
 The 245,400 persons without S&E degrees or jobs in the 1995 integrated database represent individuals who had S&E jobs in 1993, but by 1995 had moved to non-S&E jobs, become unemployed, or had moved out of the labor force. Although these cases are shown in the SESTAT integrated database, they no longer fit the population of individuals either educated in S&E or working in S&E. These individuals, along with the 334,100 persons in the 1995 integrated database without S&E degrees but still working in S&E jobs are part of a panel of individuals that are being followed throughout the 1990s. The latter group is described in figure 1 as "Box M", and is underrepresented in the SESTAT database after 1993 because the SESTAT surveys do not capture new persons entering S&E occupations who are not educated in S&E fields in this decade.
 For individuals with two or more degrees at the same highest degree level (bachelor's, master's, doctorate, professional), the field of the most recently earned degree is considered the highest degree field.
 See footnote 2.