Because of procedural changes implemented during the 1990 survey cycle to improve the completeness of race, ethnicity, and citizenship data, the data from 1990 and later years are not directly comparable to data before 1990.
In 2021, the education history section was changed to a table format in which respondents can select all the postsecondary degrees received, up to nine degrees. Based on the degrees reported, follow-up questions asked about each type of degree, including any professional doctorate being earned.
Beginning in 2021, field of study and doctorate dissertation field data are collected using a modified version of the 2020 Classification of Instructional Programs (CIP) codes. Therefore, the field of study data in 2021 may not be comparable to prior survey cycle data; see the 2021 survey cycle “Technical Notes” at https://ncses.nsf.gov/sed for more information.