In his book, Entomology and Pest Management, Larry Pedigo discusses economic thresholds and the foundation for their development and use. He states that one type of very common economic threshold is what entomologists know as the nominal threshold. A nominal threshold is one that is based upon a person's understanding of the pest's biology tied together with field experience, and it is rarely based on rigorous research. Nominal thresholds tend to be static--that is, unchanging with changes in crop value, control costs, or plant development stage.