The period spanning Reinertsen's first two books: developing-products-in-half-the-time (1991, with preston-smith) and managing-the-design-factory (1997). It follows directly from the early-career-and-engineering-background era, in which Reinertsen developed the analytical foundations at mckinsey that underpin this period's work. During this era, Reinertsen established his core frameworks: cost-of-delay, queueing-theory-applied to product development, the u-curve-optimization pattern, and batch-size-reduction. He built his consulting practice at reinertsen-and-associates, working with product development organizations. The Poppendiecks (mary-poppendieck, tom-poppendieck) discovered his work during this period and began citing it as the economic foundation of lean software development.