nsf.gov - SRS US Doctorates in the 20th Century - US National Science Foundation (NSF)

Research doctorates are differentiated by the field studied. Field of study has been a characteristic of doctorates awarded in the United States since 1861, when the first three U.S. doctorates were awarded. Those degrees, conferred by Yale, were in the fields of philosophy and languages, classics, and physics. The number of major fields and field specialties has grown to 363 since then. In this report, 12 major fields of study are used; these are categorized as either science and engineering (S&E) fields or non-S&E fields. Groupings within these two categories are shown in table 3-1

.¹

The demographic characteristics of doctorate recipients also changed substantially over the course of the century. Except in certain fields, the participation of women in doctoral education increased significantly relative to that of men. Racial and ethnic minorities also made substantial percentage gains in doctoral awards, although the absolute numbers of doctorates received by minorities remained low compared with whites. The number and percentage of doctorates awarded to non-U.S. citizens increased sharply in the 1980s and 1990s.² Other characteristics of doctorate recipients—their ages at graduation, disability status, likelihood of being married and having dependents, and the educational attainment of their parents—are also examined here.

Fields of Study

Fields of study are not static; they change as research advances the frontiers of knowledge, as shown by the influence of quantum mechanics on physics and the influence of plate tectonics on geology. New fields emerge, as computer sciences did in the last quarter of the 20th century. Many research programs have become multidisciplinary or interdisciplinary in recent decades. The federal agencies that sponsor the SED review the survey's list of field specialties annually and update it periodically. Appendix table A-1 shows the complete list of field specialties used in the SED, grouped by major field.

The distribution of doctorates across S&E and non-S&E fields reveals a stable picture. In every year from 1920 to 1999, the number of doctoral awards in S&E fields was greater than the number in non-S&E fields (table 3-2

). Of the 1,354,873 doctorates granted by U.S. institutions between 1920 and 1999, 62 percent were in major fields considered S&E and 38 percent were in fields considered non-S&E. The S&E share of degrees dropped below 60 percent only in the 1945–46 academic year, the 1970s, and the early 1980s. In 1999 U.S. institutions awarded 41,140 doctorates, 25,953 in S&E fields and 15,187 in non-S&E fields.³

Four of the top five major fields in 1995–99 were also in the top five in 1920–24, but only biological sciences held the same rank in both periods. Table 3-3

shows the top five major fields in 1920–24 and in 1995–99. The number of doctorates awarded in each major field from 1920 to 1999 is shown in figure 3-1

. Table 3-4

shows the number of doctorates awarded in each major field in 1995–99 and in 1999, as well as the peak year for each field.

Science and Engineering

Agricultural Sciences

Doctorate production in the field of agricultural sciences grew throughout the century except for small dips in the mid-1970s and the 1990s. Nonetheless, it remained the smallest S&E major field after earth, atmospheric, and ocean sciences.

Biological Sciences

Before World War II, biological sciences was one of the more rapidly growing fields in terms of the number of doctorates awarded, and it resumed its growth after the war. Subsequently, after some years of fluctuation, the field began another period of dramatic growth in the late 1980s. Biological sciences was one of the largest doctoral fields throughout the 20th century, with 167,179 doctorates awarded between 1920 and 1999.

Earth, Atmospheric, and Ocean Sciences

Lower numbers of doctorates were awarded in earth, atmospheric, and ocean sciences from 1920 to 1999 than in any other major field. Growth in doctoral awards, however, was dramatic within its detailed fields: atmospheric sciences, geosciences, and oceanography. Geosciences nearly doubled between 1960–64 and 1995–99, whereas atmospheric sciences increased sixfold and oceanography increased about ninefold (appendix table A-1).

Mathematics and Computer Sciences

Nearly all doctorates in the first two-thirds of the century in the major field of mathematics and computer sciences were awarded in mathematics. The pace of doctorate production in mathematics quickened during the 1960s, with the number peaking at 1,281 in 1972 then decreasing to fewer than 1,000 by 1977.

Until 1978 the SED had no code for computer sciences; data from 1920 to 1977 are for degrees in the field of mathematics only.⁴ Results for computer sciences show an increase in doctorates from about 200 in 1979 to almost 1,000 in 1995, after which they declined.

Physical Sciences

From 1920 until the early 1960s physical sciences led all other major fields in doctoral awards. The field's greatest growth occurred after the Soviet Union's launch of Sputnik, in 1957, and growth continued through the 1960s. Then, with deep cuts in U.S. space and energy programs in the 1970s, awards of physical sciences doctorates began to drop. Most of this decline can be attributed to chemistry, a specialty (detailed field) of physical sciences. Chemistry's share of all doctorates fell from 18 percent in 1920–24 to 5 percent in 1975–79, where it has remained. The other detailed field of physical sciences, physics and astronomy combined, also accounted for a smaller share of doctorates in the last three decades of the century, but its decline was not as severe as that of chemistry. Growth in doctorate production in physical sciences resumed in the 1980s, and a new peak was reached in 1994, after which the number of physical sciences doctorates awarded annually decreased. Between 1920 and 1999, 93,746 doctorates were awarded in chemistry, and 58,737 doctorates were awarded in physics and astronomy. Physical sciences ranked fourth in overall doctorate production during the 20th century.

Psychology

Psychology grew in doctorate production throughout the century except for a slight downturn in the late 1980s. The number of doctoral awards in psychology rose sharply after World War II and again in the 1960s and early 1970s. Unlike many of the other S&E fields, psychology did not experience declines in doctorate production during the 1970s.

Social Sciences

Social sciences remained among the top five major fields for doctorate production throughout the century. For most of the 1920–99 period, social sciences accounted for a relatively stable 9 to 11 percent of all doctorates.

Engineering

By 1995–99 engineering had replaced physical sciences among the top five major fields. From 1920–24 to 1995–99 doctoral awards in engineering rose from 60 to 29,694, or from less than 2 percent to 14 percent of all doctorates awarded. Drops in the last 3 years of the century were directly related to a decline in the number of non-U.S. citizens who received doctorates in the final years of the century.

Non-Science and Engineering

Education

The field of education produced more doctorates every year from 1962 to 1999 than any other major field. Education's share of doctorates was nearly 16 percent by 1995–99 but was greatest in the 1970s and 1980s, when it ranged from 20 to 23 percent. The number of awards remained level from the late 1980s through the end of the century.

Health Sciences

Doctorates awarded in health sciences, the smallest of the non-S&E major fields, grew from 100 in 1920–24 to 6,990 in 1995–99, and the field's share of all doctorates increased from 2 to 3 percent over that period.

Humanities

Humanities was the second largest of the major fields for production of doctorates in 1920–24 and was the fourth largest in 1995–99.

Professional and Other Fields

The number of doctorates awarded in professional and other fields grew slowly but continuously through the mid-1960s and then more rapidly through the early 1970s.⁵ Doctoral awards in these fields had another period of rapid growth in the 1980s, then began to stabilize in the 1990s.

Demographic Characteristics of Ph.D.s

Overall growth of the U.S. population naturally contributed to increases in doctorates earned over the course of the century. The demographic composition of doctorate recipients changed substantially as well. Long-term trends in the demographic characteristics of doctorate recipients—sex, citizenship status, and race/ethnicity—are examined here.⁶

Sex

Throughout the 20th century men earned the majority of doctorates and accounted for much of the substantial increase in total doctorate production (figure 3-2

). For the period 1920–99 men received 73 percent of all doctorates awarded and women received 27 percent. Most of the growth in doctorate production among men in the late 1980s and the 1990s resulted from the large increases in the numbers of foreign men seeking graduate education in the United States, not from greater numbers of U.S. men receiving doctorates. The percentage of male doctorate recipients who were foreign nationals rose from 22 percent in 1980–84 to 38 percent in 1990–94.

Changes in public policies after World War II created a more favorable climate for growth in doctorate production, noted first among men, than existed in the prewar years. In the 1950s the number of men earning doctorates surged (figure 3-2

). This trend can be largely attributed to the G.I. Bill, enacted in 1944, which afforded returning World War II veterans the opportunity and financial support to begin or continue their education. A second period of substantial growth in doctorate production by men occurred in the post-Sputnik era, from the 1960s to the early 1970s. Among the contributing factors were new or expanded federal programs for graduate fellowships and traineeships as well as student deferments during part of the Vietnam War. In the 1970s concerns about a possible oversupply of Ph.D.s led to modification or curtailment of some federal and private programs that supported graduate students, and the number of men earning doctorates declined. The end of draft deferments for graduate students in 1968 was another major factor in the sharp decline in doctoral awards to men starting in the early 1970s.

Trends in doctorate production for women were distinctly different from those for men. The period of dramatic growth in doctorates earned by women began in the 1960s and continued to the end of the century. Almost 43 percent of all doctorates awarded to women between 1920 and 1999 were awarded in the 1990s. The proportionate gains for women were truly remarkable: women's share of all doctorates conferred rose from 15 percent in 1920–24 to 41 percent in 1995–99 (figure 3-3

). Yet at the close of the century, women were still underrepresented relative to their presence in the college-educated population. In 1999 women constituted 43 percent of all Ph.D.s, compared with 48 percent of the U.S. population 25 and older with 4 years of college (U.S. Census Bureau 2000, table 251).

In 1960 women earned 1,042 doctorates; in 1999 they earned 17,493 doctorates. A convergence of influences accounts for this growth: the general increase in the young adult population as the baby boomers came of age, the women's movement, affirmative action policies, and targeted federal and private investments to increase the number of women with advanced degrees. Foreign women entering the United States for graduate education also contributed to growth in doctorate production by women. In the early 1960s 11 percent of all female Ph.D.s were foreign nationals; by the late 1990s the figure was about 21 percent.

From 1920 to 1999 more than twice as many men received S&E doctorates as received non-S&E doctorates (figure 3-4

). It was only during the last period in the century, 1995–99, that women earned more doctorates in S&E fields than in non-S&E fields. From 1920–24 to 1995–99, women's share of all S&E doctorates awarded increased from 13 to 33 percent, and women's share of all non-S&E doctorates awarded increased from 19 to 55 percent (figure 3-3

). From 1960 to 1999 the greatest percentage increase in doctorates earned by women in non-S&E fields was in health sciences, and in S&E fields it was in psychology (figure 3-5

Citizenship Status

During the last four decades of the century, non-U.S. citizens earned increasing shares of doctoral awards in each of the major fields. From 1920 to 1959 doctoral awards to non-U.S. citizens rose from 6 to 12 percent of all doctorates awarded. From 1960–64 to 1995–99, the share of doctorates awarded to foreign nationals rose from 16 to 39 percent in all S&E fields combined and from 7 to 17 percent in non-S&E fields (figure 3-6

). Most foreign nationals, both men and women, received their degrees in S&E fields.

From the mid-1980s to the end of the century, major political events were reflected in the tremendous growth in the overall number of foreign students earning doctorates in the United States. By the late 1980s about one in four Ph.D. recipients was a foreign national. This proportion rose to almost one in three in the early 1990s (figure 3-7

). Most foreign nationals who earned doctorates held temporary visas, and four in five were men.

Origins of Non-U.S. Citizens

A large majority of foreign nationals who earned U.S. doctorates between 1960 and 1999 were from Asia (figure 3-8

). During this period, China, India, Taiwan, and Korea were the top four places of origin for non-U.S. citizen Ph.D.s. Students from the People's Republic of China received more than 24,000 of the doctorates awarded by U.S. universities in the 1990s (figure 3-9

). As was true for foreign nationals overall, Asian citizens were awarded doctorates primarily in S&E fields. They received 44 percent of all engineering doctorates and 22 percent of all science doctorates conferred in 1995–99.

Trends in doctorate awards to non-U.S. citizens reflect consequences of the 1989 uprising at Tiananmen Square in Beijing, China, an event that led to the adoption of the Chinese Student Protection Act of 1992. This act made thousands of Chinese students who were enrolled in U.S. institutions in 1989 eligible for permanent residency on 1 July 1993. As a result, the percentage of Chinese Ph.D.s with temporary visas, which had been more than 95 percent in 1990, fell to a low of about 21 percent in 1995. It started to rise again in 1996, reaching 74 percent by 1999, as the pool of Chinese students eligible for permanent residency and still in graduate school diminished. Because China was the leading country of origin of non-U.S.-citizen Ph.D.s throughout the 1990s, the shift in the visa status of Chinese doctorate recipients caused a shift in the statistics for Asia as a whole. The percentage of Asian-citizen Ph.D.s with temporary visas fell from 88 percent at the beginning of the 1990s to a low of 64 percent in 1995, then rose to more than 81 percent in 1999.

With the end of the cold war came rapid growth in the number of doctorates granted to citizens of eastern European countries and the republics of the former Soviet Union (figure 3-10

). In 1995–99, 1,030 doctorates were awarded to citizens of the former Soviet Union (mostly to citizens of Russia), compared with 47 doctorates in 1990–94 and 12 doctorates in the 1980s. Citizens of Romania, Bulgaria, and the former Czechoslovakia also increased their numbers of doctorates in the late 1990s, although by a smaller amount.

Women

Between the periods 1960–64 and 1995–99, female Ph.D.s increased their presence in every citizenship group, with women's share of doctorates rising from 10 to 36 percent among permanent residents and from 9 to 24 percent among temporary residents, but rising most noticeably among U.S. citizens. Women made up 47 percent of all U.S.-citizen Ph.D.s in 1995–99, a greater than fourfold increase from 1960–64 (11 percent). U.S. women made notable gains in both S&E and non-S&E major fields during the same period, increasing their share of all S&E doctorates awarded to U.S. citizens from 7 to 39 percent and their share of non-S&E doctorates from 17 to 57 percent (figure 3-11

Race/Ethnicity

From 1975, when data on race/ethnicity were first collected in the SED, to 1999, three groups accounted for almost 90 percent of all doctorates awarded in the United States: white U.S. citizens (68 percent), Asian foreign nationals (14 percent), and white foreign nationals (8 percent). Minority U.S. citizens accounted for most of the remainder: blacks (3 percent), Asians/Pacific Islanders (2 percent), Hispanics (2 percent), and American Indians/Alaskan Natives (0.3 percent).⁷ The largest Hispanic subgroup among Hispanic Ph.D.s was Other Hispanic, followed by Mexican American and Puerto Rican (figure 3-12

). According to a study of Hispanic Ph.D.s from 1983 to 1997, the subgroup Other Hispanic also ranked first in shares of S&E doctorates, followed by Puerto Rican and Mexican American (Quintana-Baker 2002).

Of doctorates awarded to U.S. citizens, the share earned by members of minority groups increased from 8 percent in 1975–79 to 14 percent in 1995–99 (figure 3-13

). The number of awards to minorities remained relatively low despite high proportionate gains. Between 1975–79 and 1995–99 the number of doctorates earned by Asians/Pacific Islanders who were U.S. citizens increased over threefold, from 1,777 to 6,039 degrees, and the number of doctorates earned by U.S. citizens who were members of underrepresented minorities (American Indians/Alaskan Natives, blacks, and Hispanics) nearly doubled, from 7,644 to 13,176 (figure 3-14

Minorities received almost 14 percent of all S&E doctorates awarded to U.S. citizens in 1995–99, up from 6 percent in 1975–79. Between 1975–79 and 1995–99 the percentage growth in S&E doctoral awards to U.S. citizens was greater for minorities than for whites, and growth in awards to minority citizens in S&E fields was somewhat greater than growth in awards to minorities in all fields combined. By 1995–99 a majority of Ph.D.s in every racial/ethnic group except blacks were in S&E fields, with Asians/Pacific Islanders having the largest proportion of Ph.D.s in S&E fields (table 3-5

Minority citizens earned more than 14 percent of the non-S&E doctorates awarded to U.S. citizens in 1995–99, up from about 10 percent 20 years earlier (figure 3-15

). In 1995–99 blacks accounted for more than half of the non-S&E doctorates earned by minorities and more than 7 percent of all non-S&E doctorates awarded to U.S. citizens. Blacks received more than one-tenth of all education doctorates in 1995–99 and also received larger shares of degrees in health sciences and professional and other fields than were received by members of other minority groups (figure 3-16

). Hispanics earned the largest share of humanities doctorates (nearly 4 percent) among minorities.

Over the last quarter of the century, the share of Ph.D.s earned by women increased in every racial/ethnic group among U.S. citizens (figure 3-17

). Women's share of doctorates earned in 1995–99 was largest among blacks (nearly 62 percent) and smallest among Asians/Pacific Islanders and whites (43 percent and 46 percent, respectively). Women earned slightly over half of all doctorates awarded to Hispanics and slightly under half of all doctorates awarded to American Indians/Alaskan Natives.

Age

Variations in the age at which persons receive the doctorate reflect many factors, including field of study, sex, age at baccalaureate graduation, the time it takes to complete requirements for the doctorate, and educational and career choices made at different stages, which may postpone or interrupt the path to the doctorate.

When students pursue their undergraduate education on a part-time basis, they are likely to take longer than 4 years to earn the bachelor's degree. If a substantial number of students follow this pattern, the average age of baccalaureate recipients, and hence doctorate recipients, will rise. Moreover, many students who eventually pursue a doctorate do not enter graduate school immediately after receiving a bachelor's or master's degree. Many graduates enter the workforce and only later decide to undertake doctoral studies. In some fields, such as education, specific kinds of work experience may be required before the doctorate is awarded. These factors, among others, contribute to the total elapsed time between receipt of the baccalaureate and receipt of the doctorate.

During the 1950s and 1960s, concerted efforts were made to reduce the time required to earn a doctorate, and the data indicate that there were declines in the age of new Ph.D.s during that era. Between 1970 and 1999, however, the age of Ph.D.s at graduation rose (figure 3-18

). Doctoral students graduating in 1995–99 were, on average, nearly 34 years old, almost 2 years older than those graduating in 1960–64. Reflecting variations by field, recipients of doctorates in S&E fields were substantially younger than their non-S&E colleagues throughout this period, and the differences in their ages increased beginning in 1975–79.

Over the 40-year period from 1960 to 1999, the difference between the ages of men and women at graduation narrowed. In 1960–64 female Ph.D.s were almost 5 years older than male Ph.D.s, but by 1995–99 the gap between the average ages of male and female Ph.D.s was less than 2 years (figure 3-19

Disability Status

Statistics on the disabilities of Ph.D. recipients began being collected in the SED in 1993. Nearly 4,700 individuals with self-reported disabilities were awarded doctorates between 1993 and 1999—accounting for close to 2 percent of all doctorates awarded in that period, substantially below the percentage of disabled persons in the U.S. population. In 1997 about 13 percent of the U.S. population 22 to 44 years old had some kind of disability, and nearly 8 percent were severely disabled (U.S. Census Bureau 2000, table 222).

Among Ph.D.s graduating in 1993–99, orthopedic (mobility) disabilities were the most common, reported by 28 percent of those with disabilities, followed by visual (19 percent) and auditory (14 percent) disabilities. Very few of these new graduates had vocal disabilities (figure 3-20

Marital Status and Dependents

Overall, individuals who earned doctorates at the end of the century were less likely to be married or to have dependents (children or adult dependents) than were those who graduated 40 years earlier. In every 5-year period from 1960–64 to 1995–99, a majority of Ph.D.s were married at the time of their graduation; however, the proportion of married graduates fell from about 75 to 60 percent between the early 1960s and late 1990s. (figure 3-21

). Men were more likely than women to be married, but this gap began to narrow in the 1980s. Although the percentage of graduates who were married has decreased both overall and among U.S. citizens since 1960–64, particularly among men, it has increased slightly among permanent and temporary residents (figure 3-22

The percentage of Ph.D.s (regardless of marital status) who had dependents at the time the doctorate was received declined from 76 percent in 1960–64 to 48 percent in 1995–99, with men in both periods being more likely than women to have dependents (figure 3-23

). Women who received doctorates in 1995–99 were more likely to be married and to have children or other dependents than were women who graduated in 1960–64 (figures 3-22

, 3-23

). Declines in both married graduates and graduates with dependents were greater among recipients of doctorates in S&E fields than among those who received doctorates in non-S&E fields.

The percentage of Ph.D.s who were married at the time of their graduation declined in every U.S. racial/ethnic group after 1975–79 (figure 3-24

). The percentages of whites and American Indians/Alaskan Natives who were married stabilized in the 1980s, but the percentages of married Asians/Pacific Islanders, blacks, and Hispanics were still falling at the end of the century.

Parents' Education

Rising educational attainment in the U.S. population as a whole is reflected in the Ph.D. population. Data on the educational attainment of the parents of Ph.D.s became available in 1965. On the whole, the level of educational attainment for families of doctorate recipients is higher than the national average. By 1995–99 more than one-third (nearly 35 percent) of new Ph.D.s came from families in which both the mother and the father had a college degree (figure 3-25

). Nearly half of doctorate recipients in 1999 had a parent who held a bachelor's or advanced degree, compared with less than one-fifth of parent equivalents (those 55 or older, the assumed age of Ph.D.s' parents) in the U.S. population (figure 3-26

). In contrast, 30 years earlier, almost half of new Ph.D.s came from families in which neither parent had attended college. Among doctorate recipients in general, the father's educational level was higher than the mother's (figure 3-27

References

National Science Board (NSB). 2002. Science and Engineering Indicators 2002. 2 vols. NSB-02-1. Arlington, VA: National Science Foundation.

National Science Foundation (NSF). 2002. Science & Engineering Degrees, 1966–2000, table 46. NSF 02-327. Arlington, VA.

Quintana-Baker, M. 2002. A profile of Mexican American, Puerto Rican, and other Hispanic STEM doctorates: 1983–1997. Journal of Women and Minorities 8:99–121.

U.S. Census Bureau. 2000. Statistical Abstract of the United States: 2000. 120th ed., tables 222, 251. Washington, DC.

1 The NSF classification scheme used for this report groups health sciences with humanities, education, and other professional fields in the broad area of non-S&E. A detailed listing of doctoral degrees awarded by field can be found in appendix A and with the supplemental tables for this report, available on the NSF website at http://www.nsf.gov/statistics/nsf06319/. Other agencies and organizations include health sciences with biological and agricultural sciences in a "life sciences" cluster or combine health sciences with biological sciences to create a "biomedical sciences" cluster.

2 Data in chapters 3 through 6 are taken from the Doctorate Records File and thus date from 1920. Although Survey of Earned Doctorates (SED) data were collected first in the 1957–58 academic year (referred to as 1958 in published reports), the trends based exclusively on SED data are discussed in 5-year cohorts beginning with 1960. Data are grouped in 5-year intervals for ease of discussion and to permit "smoothing" of data for small groups.

3 In 1999 European universities conferred 54,000 S&E doctorates, and Asian universities conferred 21,000 S&E doctorates. European universities awarded more doctorates than either the United States or Asia in each of the broad areas of S&E. U.S. universities conferred more doctorates in all science fields in 1999 than did Asian universities but conferred fewer in engineering (NSB 2002, 1:2-41–2-42).

4 The National Center for Education Statistics (NCES), U.S. Department of Education, began collecting data from institutions on the field of computer science a decade earlier than the SED did. NCES data show 196 doctorates in computer science in 1978, numbers considerably higher than the 1978 SED number of 121 (NSF 2002, table 46).

5 This major field includes doctorates in business management and administrative services, communications, and other professional fields, such as architecture and environmental design, library science, public administration, and social work.

6 A listing of the country of citizenship of non-U.S. citizen Ph.D.s by visa status can be found with the supplemental tables for this report on the NSF website at http://www.nsf.gov/statistics/nsf06319/.

7 Discussions of race/ethnicity in this report refer to U.S. citizens only unless stated otherwise.

Chapter 3. Field Choices and Demographic Characteristics of Doctorate Recipients

Highlights

Introduction