Definitions from gpt4o:

U-1: The percentage of the labor force unemployed for 15 weeks or longer. This is a very narrow measure focusing on long-term unemployed individuals.

U-2: The percentage of the labor force who lost jobs or completed temporary jobs. This also focuses on job losers, particularly those who may face short-term unemployment.

U-3: The official unemployment rate, which represents the total number of unemployed people actively seeking work as a percentage of the labor force. This is the most commonly reported unemployment figure.

U-4: Includes U-3 but adds “discouraged workers”—individuals not currently looking for work because they believe no jobs are available for them or there are none for which they qualify.

U-5: Includes U-4 and adds other “marginally attached workers”—those who are not looking for work for various reasons (such as school or family responsibilities) but still want and are available for a job.

U-6: The broadest measure, which includes U-5 and adds people working part-time for economic reasons. This group includes those who are working fewer hours than they would like or in part-time positions due to economic constraints.

Record would stem after 1994 - when major redefinitios of unemployment occurred