The current economic crisis, a growing workforce, the increasing lifespan of workers, and demanding, complex jobs have made organizations highly selective in employee recruitment and retention. It is therefore important, to the adult educator, to develop models of learning that better prepare adult learners for the workplace. The purpose of this study was to expand upon previous research by exploring sociodemographic and occupational variables, including survey participant background, employment, household characteristics, education, training, and career field independent variables, that could form unique combinations to best predict participation in workplace learning and individual earnings. The study compared the results of multiple administrations of adult education surveys to determine if the unique combinations of independent variables change over time, and assessed independent and dependent variables within a context of workplace learning theory to examine the relationships between survey variables and learning theories. The study involved analysis from the 1995, 1999, 2001, 2003, and 2005 National Household Education Surveys on Adult Education. Descriptive, bivariate, binomial, and multivariable regression spline analyses were used to examine the relationships between the sociodemographic and occupational characteristics of survey respondents who reported participation in formal and informal work-related learning activities. The results of the study indicated that there were statistically significant predictive effects on formal and informal learning methods by the sociodemographic and occupational characteristics of survey participants, and indicated that the effects of age, education, sex, experience, marital status, race/ethnicity, earnings, and geographic location, to varying degrees, influenced the outcomes of work-related learning. Higher levels of education, learning and income supported increased likelihoods of participation in formal and informal learning activities throughout the survey participants' career and beyond. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]