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0N TI~E T0 THE DOCTORATE A Study of the Increased Time to Complete Doctorates in Science and Engineering Howard luckman Susan Coyle Span Bee ~0~ ACHES Pat Washing10n, O.C. 1990

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NOTICE: lbe project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The survey project is part of the program of the Office of Scientific and Engineering Personnel (OSEP). This report has been reviewed by a group of persons other than the author according to procedures approved bv a Report Review Committee consisting of members of the National ~ - r ~ ~ v Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Frank Press is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the chatter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal govemment. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Robert M. White is the president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Samuel O. Thier is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and of advising the federal government. Functionin& in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Frank Press and Dr. Robert M. White are the chairman and vice-chairman, respectively, of the National Research Council. This report is based on research conducted by OSEP, with the support of the National Science Foundation, under NSF Contract No. PRA-87 19855. Opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the sponsoring agencies. Library of Congress Catalog Card No. 89-62949 Intemational Standard Book Number 0-309-04085-X Additional copies of this report are available from: S010 Printed in the United States of America National Academy Press 2101 Constitution Avenue, N.W. Washington, D.C. 20418

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PREFACE A need exists for better models of what contributes to changes in the time that students take to complete the doctorate. Although time to the doctorate has been studied by Abedi and Benkin (1987), Berelson (1960), Prior (1962), and Wilson (1965), none of these studies are based on a causal model of student decisionmaking, and none consider the role of market forces in student decisions. The data presented in Chapter 1 suggest that time to the doctorate in science and engineering fields has been lengthening since 1967- in some fields, by as much as two years. Furthermore, it is anticipated that the lengthening mend will persist, at least into the near future, and have unfortunate consequences because of the decline in the college-age population and the dramatic increase expected in the number of job openings in the academic sector in the 1990s. In response, public policy makers are likely to become increasingly concerned with identifying and understanding ways to augment the supply of new doctorates. While shortages of this type are not expected for a few years, it is useful now to determine whether policies can be adopted that can limit or reverse the trend toward longer completion times in the science and engineering fields. Existing studies do not provide the information needed by policy makers to detains whether public policy could, or should, alter completion times sufficiently to slow or reverse the trends discussed in Chapter 1, or whether any policies can have a major impact on supply in the impacted fields. The purposes of the present study are to render an in-depth analysis of what has happened to completion times since 1967, to provide a time-series data base for the period 1967-1986, and to develop a model that explains some of the factors that have caused an elongation to occur. This study looks at the effects of changes in five types of variables: family background characteristics, student attributes, financial aid, institutional environment, and market forces. Using data from the Doctorate Records File and the Survey of Doctorate Recipients maintained by the Office of Scientific and Engineering Personnel (OSEP) of the National Research Council and from other data sources,* the study develops a model to explain changes in both total time to the doctorate (TTD) and in the * A more detailed description of the data from these sources is available on request from the National Research Council, Office of Scientific and Engineering Personnel. iii

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several components of time to the doctorate. The model is then applied to 11 scientific and engineering fields: chemistry; physics and astronomy; earn, atmospheric, and marine sciences; mathematical sciences (including computer and information sciences); engineering; agricultural sciences; biological sciences; health sciences; psychology; economics; and all other social sciences. This report is organized as follows. Chapter 1 begins with an examination of how and when time to the doctorate has been lengthening, illustrated by the rise in mean AD from 1967 to 1986 in each of the 11 fields. Three components of AD are introduced, and the mean values for each are presented and discussed. In addition, time coefficients allow one to contrast the way in which time to the doctorate has changed during the period, and two patterns of change are identified. Finally, quantitative estimates are provided of the person-year losses that society has incurred from the lengthening of completion time during this period. Chapter 2 reviews five avenues of inquiry in the literature as they relate to time to the doctorate and models of student decisionmaking. Chapter 3 introduces a causal model of the determinants of T1D based on an opportunity-cost framework of student decisionmaking. The role of financial aid and of market forces is explored in this context. Chapter 4 presents selected data on the zero-order correlations between the independent variables in the model and lend (and its components). The correlations among the salary variables and unemployment/employment plans variables are discussed, and the contribution of each major vector (e.g., family background and student attributes) is examined. Chapter 5 introduces the statistical model and presents a summary of which regression coefficients are significant (and of their signs) for alternative specifications of the model. Several variants of the model are introduced to explore the effects of alternative measures of the key variables. Chapter 6 presents the regression coefficients for the basic model and several variants using registered time to the doctorate (RTD) as the dependent variable. Finally, Chapter 7 discusses the findings in this study, their implications, and research questions that warrant further study. In addition, an extensive bibliography of readings on the determinants of student decisionmaking is provided (pp. 107-111~. Appendix A (pp. 113-173) provides additional tables about (1) the components of HID, (2) the person-year losses resulting from a lengthening of Fold, (3) variables in the model, (4) zeros order correlations among the independent variables, (5) several equations for estimating HID, and (6) median total time to doctorate for the population as a whole and for selected demographic groups. Finally, acronyms used throughout this report are listed in Appendix B (pp. 175-177~. Staff Howard Tuckman, consultant Susan Coyle, staff officer 1V Yupin Bae, research associate Linda S. Dix, editor

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CONTENTS EXECUTIVE SUMMARY Findings Conclusions 1 WHAT HAS BEEN HAPPENING TO TIME TO THE DOCTORATE? Components of Time to the Doctorate and How They lIave Changed Through Time The Several Kinds of Time Mean Total Time to the Doctorate Mean Time Spent Prior to Graduate School Enhance Mean Registered Time to the Doctorate Mean Time Spent Away Tom the University Summary The Nature and Significance of the Time Trend The Two Models Patterns of Change The Shape of Change Manpower Loss from Lengthening Total Time to the Doctorate 2 MODELS OF THE FACTORS THAT AFFECT STUDENT CHOICE AND TIME TO THE DOCTORATE: A LITERATURE SURVEY Literature on Persistence and Attntion Literature on Educational Aspirations Literature on Enrollments Literature on Expected Returns Literature on TTD Summary 3 A MODEL OF THE DETERMINANTS OF TTD The Model The Critical Role of Opportunity Costs v 1 4 7 8 8 9 12 12 12 13 13 13 14 19 19 25 25 28 29 31 32 33 35 35 36

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Financial Aid and Its Impact on Completion Times The Impact of Type of Aid Effects on He Components of AD Market Forces and Completion Times Effects of Changes in Relative Salaries Effects of Employment Opportunities Effects on the Components of 1TD The Variables Used to Develop He Model THE RELATION BETWEEN THE FIVE VECTORS OF VARIABLES AND TTD AND ITS COMPONENTS: A COMPARISON OF ZERO-ORDER CORRELATIONS The Importance of Disaggregation by Field Changes in Family Background Characteristics Changes in Student Attributes Changes in Tuition and Financial Aid Changes in Institutional Environment Changes in Market Forces Salary Variables Employment Indicator Variables The Stock Variable The Zero-Order Correlation of the Vectors Summary 5 CHANGES IN TTD Common Variables Model Log Linear Equations Weaknesses of the Common Variables Model Unique Variables Model Summary of Findings Limitations of the Analysis What Can Be Learned from He Findings? 6 CHANGES IN REGISTERED TIME TO THE DOCTORATE TIME PRIOR TO GRADUATE ENTRANCE, AND TIME NOT ENROLLED IN THE UNIVERSITY Registered Time to the Doctorate RTD in the Common Variables Model Using Linear and Log Linear Equations RTD in the Unique Variables Model Evaluation of the Results Time Spent Prior to Graduate School Entrance (TPGE) Time Not Enrolled in the University (TNEU) Summary of the Findings V1 38 38 39 41 41 42 43 43 45 45 46 46 51 51 56 56 60 60 65 67 69 69 71 71 71 71 73 77 79 79 79 79 81 85 87 89

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7 PAST AS PROLOGUE What Has Happened to Time to the Doctorate? Total Time to the Doctorate Registered Time to the Doctorate Variation Around the Mean Could Changes in I-POE and TNEU Have Been Large Enough to Explain the Change in TTD? Possible Explanations Epistemic Explanations Institutional Explanations Student Preference-Based Explanations Financial Need-Based Explanations Demographic and Ability-Based Explanations Mbrket-Based Explanations Is There A Single Explanation for Increase in TTrL,? Implications of a Continuing Rise in TTD A More Resource-Intensive Doctoral Program A Longer Gestation Period Increased Attntion Lower Returns for Graduate Study Changes in the Attractiveness of Alternative Doctorate Careers i~~ as a Policy Instrument SELECTED BIBLIOGRAPHY APPENDIXES A Related Tables B List of Acronyms LIST OF TABLES 1.1 The Relationship Between the Several Time Measures 1.2 Estimated Time Trends in Mean Total Time to Doctorate 1.3 Estimated Time Trends in Mean Registered Time to Doctorate 1.4 Estimated Time Trends in Mean Time Prior to Graduate Entrance 1.5 Estimated Time Trends in Mean Time Not Enrolled in University 1.6 Difference Between Forecast and Actual TiDs, 1987 1.7 Maximum Potential Person-Years Loss Resulting from Lengthening Total Time to the Doctorate, 1968-1986 93 93 93 94 95 96 97 97 97 98 99 100 101 101 102 102 103 104 105 105 105 107 113 115 175 9 15 16 17 18 22 22 3.1 Mean Time to the Doctorate, by Primary Source of Support, 1986 and 1987 40 4.1 Correlation for Percent Married, 1967-1986 47 4.2 Correlation for Average Number of Dependents, 1967-1986 47 4.3 Correlation for Percent Black, 1974-1986 48 4.4 Correlation for Percent Hispanic, 1974-1986 48 . . V11

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Correlation for Percent Female, 1967-1986 Correlation for Average Age at Start of Doctoral Program, 1967-1986 4.7 Correlation for Percent From Selective Undergraduate Schools, 1967-1986 Correlation for Percent with Undergraduate Degree in Doctoral Field, 1974-1986 4.9 Correlation for Average Tuition Paid 4.10 Correlation for Percent with Primary Support from Federal Government, 1967-1986 4.11 Correlation for Percent with Primary Support from Private Foundations, 1967-1986 Correlation for Percent with Primary Support from Research Assistantships, 1967-1986 Correlation for Percent with Primary Support from Teaching Assistantships, 1967-1986 4.14 Correlation for Percent with Primary Support from Own Eamings, 1977-1986 4.15 Correlation for Percent with Baccalaureate from Foreign Institutions, 1967-1986 4.16 Correlation for Number of Full-Time Equivalent Faculty 4.17 Correlation for Government R&D Spending 4.18 Correlation for Percent with Baccalaureate from Category I - Research University, 1967-1986 4.19 Correlation for Percent with Baccalaureate from "Top 40" School, 1967-1986 Correlation for Percent with Graduate Degree from Category I or Category II Research School, 1967-1986 Correlation for Percent with Graduate Degree from "Top 40" School, 1967-19g6 Correlation for Average Salary of Recent Doctorate Recipients Correlation Between SALRAT1 and rl~l L) and Its Components Correlation for Salary Ratio of Doctorates 10 Years After Degree Correlation Between SDR Salaries and Salaries Reported by Other Sources, 1968-1986 Correlation for Percent Seeking Postgraduate Employment Correlation for Percent with Dehlnite Employment or Postdoctoral Appointment Correlation for Overall U.S. Unemployment Rate Correlation for Unemployment Rate of College-Educated Population . . . vail 49 49 50 50 51 52 52 53 53 54 54 55 55 57 57 58 58 59 59 60 61 62 62 63 63

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4.30 Correlation Between Percent Seeking Postgraduate Employment and the Other Market Variables 4.31 Correlation for Per Capita Number of Doctorates in the United States, 1967-1986 4.32 Amount of Adjusted Variation in TTD Explained by Each of the Five Vectors 4.33 Number of Fields in Which Each Vanable Had a Statistically Significant Correlation with TTD or RTD 5.1 Summary of Common Linear Model Regression Results for TTD, by Variable 5.2 Summary of Common Log-Linear Model Regression Results for TTD, by Variable 5.3 Summary of Unique Variables Model Regression Results for TTD, by Field 5.4 Number of Fields in Which Variable Has Statistically Significant Effect on I-l L, 6.1 Summary of Common Linear Model Regression Results for RTD, by Field 6.2 Summary of Common Log-Linear Model Regression Results for RTD, by Field 6.3 Summary of Unique Variables Model Regression Results for RTD, by Field 6.4 Number of Fields in Which Variable Has Statistically - Significant Effect of TTD 6.5 Summary of Common Linear Model Regression Results for TPGE, by Variable 6.6 Summary of Common Log-Linear Model Regression Results for TPGE, by Variable 6.7 Summary of Common Linear Model Regression Results for TNEU, by Variable 6.8 Summary of Common Log-Linear Model Regression Results for TNEU, by Field 7.1 Median Total Time to the Doctorate Over Time LIST OF FIGURES Median years to the doctorate, all fields combined including humanities and education fields, 1958-1986 Components of mean total years to the doctorate, by field, 1967 and 1986 Mean total time to the doctorate, by field, 1967-1986 1X 64 64 65 66 70 72 74 76 80 81 82 84 86 88 89 90 94 7 10 20

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