Many congressional policymakers have an ongoing interest in whether the number of U.S. scientists and engineers is sufficient to meet the needs of U.S. employers, to spur economic growth and job creation through innovation, to maintain U.S. global technological leadership and industrial competitiveness, and to address other important national and societal needs. To help ensure an adequate science and engineering (S&E) workforce, Congress has established and funded a variety of federal programs. These programs are intended to foster improved science, technology, engineering, and mathematics (STEM) skills among students; to incentivize students to pursue degrees in science and engineering through tools such as fellowships, assistantships, and traineeships; and to provide graduate and postgraduate research experiences at U.S. colleges and universities through the financing of university-based research. The 115 th Congress is considering a wide variety of legislation to promote STEM education. In addition, Congress is considering changes to immigration policies, among them the number of visas and processes associated with F-1 visas, H-1B visas, L-1 visas, and legal permanent residency ("green cards"), to address U.S. S&E workforce needs. As Congress develops policies and programs and makes appropriations to help address the nation's needs for scientists and engineers, it may consider past, current, and projected S&E workforce trends. Among the key factors that labor economists examine for evidence of labor shortages are employment growth, wage growth, and unemployment rates relative to other occupations. This report provides employment, wage, and unemployment information for the computer occupations, mathematical occupations, engineers, life scientists, physical scientists, and S&E management occupations, as follows: The section on " Current Employment, Wages, and Unemployment " provides a statistical snapshot of occupational employment, wage, and unemployment data for the S&E workforce in 2016 (the latest year for which data are available). The section on " Recent Trends in Employment, Wages, and Unemployment " provides a perspective on how S&E employment, wages, and unemployment changed during the period 2012-2016. The section on " Employment Projections, 2016-2026 " provides an analysis of projections by the Bureau of Labor Statistics for how the number employed in S&E occupations is expected to change during the 2016-2026 period, as well as how many openings will be created by growth, labor force exits, and occupational transfers. A final section, " Concluding Observations ," provides stakeholder perspectives that Congress may consider as it seeks to ensure that the United States has an adequate S&E workforce to meet the demands of the 21 st century. Most experts agree that there is no authoritative definition of which occupations comprise the science and engineering (S&E) workforce. Rather, the selection of occupations included in any particular analysis of the S&E workforce may vary. Some analysts, policymakers, and organizations may refer to the group in different ways (e.g., the scientific and technical workforce, the STEM workforce) and include varying sets of occupations. In 2011, the Bureau of Labor Statistics (BLS), in defining the STEM occupations for a particular analysis, stated, "This is only one possible definition of STEM occupations; other definitions exist that may be better suited for other uses." The size of the S&E workforce varies substantially depending on which occupations are included in the definition. In its 2016 Science and Engineering Indicators report, the National Science Board (NSB) stated, "In 2013, estimates of the size of the S&E workforce ranged from approximately 6 million to more than 21 million depending on the definition used," further noting that "when defined by occupation, the S&E workforce totals between 6.2 million and 6.3 million people according to the most recent estimates." The policy debate about the adequacy of the U.S. S&E workforce has focused largely on the computer occupations, mathematical occupations, engineers, and physical scientists. For purposes of this report, these occupations, along with life scientists (a part of the natural sciences, with physics and chemistry) and S&E management occupations, are collectively referred to as the S&E workforce. Notably, this group does not include social scientists (e.g., economists, survey researchers, psychologists, sociologists, urban and regional planners, anthropologists, archeologists, geographers, historians, political scientists) or S&E-related technicians. As defined this way, the size of the S&E workforce in 2016 was approximately 6.9 million. This report uses a modified version of the Standard Occupation Classification (SOC) system to categorize scientists and engineers. The report taxonomy includes six S&E occupational groups, each composed of closely related detailed occupations: Computer occupations— computer and information research scientists; computer systems analysts; computer programmers; software developers, applications; software developers, systems software; database administrators; network and computer systems administrators; computer user support specialists; computer network support specialists; information security analysts; web developers; computer network architects; and computer occupations, all other. Mathematical occupations— actuaries; mathematicians; operations research analysts; statisticians; and mathematical science occupations, all other. Engineers— aerospace, agricultural, biomedical, chemical, civil, computer hardware, electrical, electronics (except computer), environmental, health and safety (except mining safety engineers and inspectors), industrial, materials, mechanical, mining and geological (including mining safety engineers), nuclear, and petroleum engineers; engineers, all other; and marine engineers and naval architects. Life scientists— animal scientists; food scientists and technologists; soil and plant scientists; biochemists and biophysicists; microbiologists; zoologists and wildlife biologists; biological scientists, all other; conservation scientists; foresters; epidemiologists; medical scientists (except epidemiologists); and life scientists, all other. Physical scientists— astronomers; physicists; atmospheric and space scientists; chemists; materials scientists; environmental scientists and specialists (including health); geoscientists (except hydrologists and geographers); hydrologists; and physical scientists, all other. Science and engineering managers— computer and information systems managers, architectural and engineering managers, and natural sciences managers. A description of the detailed occupations is provided in the Appendix A . Figures illustrating the educational composition of each S&E occupation are provided in Appendix B . This report relies on federal government employment, wage, and unemployment data from the following sources: The Occupational Employment Statistics (OES) , a survey of nonfarm establishments conducted by the U.S. Department of Labor's Bureau of Labor Statistics and state workforce agencies, is the source of employment and wage data for the 2012-2016 period. The survey provides employment and wage estimates annually for over 800 occupations. According to BLS, "employees" are all part-time and full-time workers who are paid a wage or salary. The survey does not cover the self-employed, owners and partners in unincorporated firms, household workers, or unpaid family workers. For this report, the wage statistic used is the occupational "mean wage," an average wage calculated by summing the wages of all the employees in a given occupation and then dividing the total wages by the number of employees. The Current Population Survey (CPS) , a monthly survey of households conducted for BLS by the Department of Commerce's Bureau of the Census, is the source of the unemployment data in this report. CPS data are also used to supplement OES data in BLS employment projections (discussed below). BLS's Employment Projections , a biennial product of BLS, provide occupational employment and industry employment projection data for 10-year periods. The latest projections, covering the 2016-2026 period, were published in October 2017. According to BLS, for most industries, the OES survey provides data for the occupational staffing patterns—the distribution of wage and salary employment by occupation in each industry—and Current Employment Statistics (CES) data provide information on total wage and salary employment in each nonfarm industry. While OES data include only wage and salary, nonfarm employment, the employment data in the projections also include agricultural industry employment and the self-employed (derived from CPS data) to arrive at base year employment levels for each occupation. The " Recent Trends in Employment, Wages, and Unemployment " section provides information on changes in employment, wages, and unemployment for the period 2012 to 2016. The " Employment Projections, 2016-2026 " section relies entirely on the most recent Bureau of Labor Statistics biennial employment projections for the 2016-2026 time frame. It is important to note that a wide range of factors can affect the size and occupational composition of the U.S. S&E workforce. Among these factors are global and domestic economic conditions; the development and market adoption of new technologies; capital cost and availability; the level of public and private funding for research and development; changes in scientific, technological, and market opportunities; the size, knowledge, and skills of the U.S.-born labor force; the size, knowledge, and skills of the foreign-born labor force in the United States; and changes in business practices regarding the use of foreign-based science and engineering capabilities. This report does not attempt to attribute changes in the U.S. S&E workforce to any of these factors specifically. In addition, a variety of factors may affect the comparability of OES data over time: Although the OES survey methodology is designed to create detailed cross-sectional employment and wage estimates for the U.S., States, metropolitan and nonmetropolitan areas, across industry and by industry, it is less useful for comparisons of two or more points in time.