• Reliability - Daubert provides four flexible factors to determine if the evidence qualifies as reliable:  testing, peer review and publication, error rates, and general acceptance in the relevant community.  As updated by Kumho, the Court stressed that not all factors may apply with every case, especially in the social sciences.  The trial court is left as the gatekeeper using the factors as flexible guidelines to assure the expert employs the same level of intellectual rigor as he or she would outside the courtroom when working in the relevant discipline.  The applicability of each of the four factors is discussed below.
  • Testing - The scientific testing criteria is directed more toward the “hard” sciences (e.g. engineering) than toward vocational and economic testimony, since such testimony is concerned with the future experience of people, which can never be tested or known with absolute certainty.  Data from the Current Population Survey (CPS), however, are produced and extensively tested by the U.S. Census Bureau and the U.S. Bureau of Labor Statistics.  The probabilities of life are drawn from the life tables from the U.S. Department of Health and Human Services, National Center for Health Statistics, which produces and extensively tests the tables.
  • Peer Review and Publication – Worklife tables and the CPS data used to measure employment rates of persons with a work disability are the subject of multiple articles.  The bibliography is a partial listing of these articles and includes listings of articles pertaining to the worklife tables themselves, the methodology underlying The Tables, and the use of CPS data for government and nonforensic researchers.  The bibliography shows that the worklife tables have been reviewed in professional journals and that the CPS data have been used by researchers for both forensic and non-forensic purposes. 
  • Error Rates - This criterion is primarily intended to apply to the “hard” sciences in conjunction with the testing performed there (e.g., reliability of a bolt securing a heavy sheet of metal).  With regard to standards for controlling the technique’s operation, the LPE methodology used to develop the tables was developed by Brookshire and Cobb (1983).  It was further refined by Brookshire, Cobb, and Gamboa (1987) to adjust for work disability, and is one of multiple widely accepted methods to compute worklife expectancies discussed in Life and Worklife Expectancies (Richards & Abele 1999).  
  • General Acceptance – Forecasting a plaintiff’s future earnings stream is not an exact science.  There is no single step in the loss computation process that enjoys universal acceptance in the relevant community.  As such, it is predictable that experts will disagree on the method for computing lost earnings.  This is true of defining earning capacity, computing worklife expectancy, projecting earnings growth, and determining discount rates.

The U.S. Supreme Court recognized the inexact nature of assessments for lost earnings in its 1983 decision in Jones and Laughlin Steel Corporation v. Howard E. Pfeifer 462 U.S. 523.  The Court stated that

by its very nature the calculation of an award for lost earnings must be a rough approximation.  Because the lost stream can never be predicted with complete confidence, any lump sum represents only a ‘rough and ready’ effort to put the plaintiff in the position he would have been in had he not been injured. 

However, there is wide acceptance of use of the CPS data to define work disability.  In addition, a 1999 publication by Richards and Abele, Life and Worklife Expectancies, looks at several generally accepted ways of computing a statistical worklife, including the method used in The New Worklife Expectancy Tables. 

The methodology used to develop The Tables was developed by Michael Brookshire and William Cobb and was further refined by Brookshire, Cobb, and Anthony Gamboa.  In a 1991 article in the Journal of Legal Economics, Gary Albrecht applied this methodology to assessments of earnings for partially disabled individuals.  The opinions expressed by users of the worklife tables are consistent with this methodology. 

The worklife tables and the methodology underlying them have been the subject of many articles, lending credence to their overall acceptance.

• Relevancy – The CPS data used in The Tables are averages for the applicable disability population – those people with a work disability.  For forensic purposes, when assessing loss of lifetime earnings, the most relevant and direct focus is on persons who have a work disability. 

Averages from various populations have long been accepted as a means for prediction – life expectancy, earnings, and others – and have long been accepted for use in the courts.  No statistic, no matter how fine-tuned, can provide an exact predictor of an individual’s future.  This is as true of worklife expectancies as it is of various measures of annual earnings, growth rates, and discount rates. 

Experts, however, must not blindly apply data to a plaintiff without consideration of how it matches the plaintiff’s circumstances.  The expert must apply data from The Tables with intellectual rigor, applying the available statistics about the work-disabled population and molding them to meet the specifics of the case.  If the plaintiff is unlike the statistical cohort, the statistic should be adjusted, or the analysis of lost earnings should be presented in a range, using two different worklife expectancies.