Continuous customer-centric requirements reprioritization is essential in successfully performing agile software development. Yet, in the agile RE literature, very little is known about how agile reprioritization happens in practice. Generic conceptual models about this process are missing, which in turn, makes it difficult for both practitioners and researchers to reason about requirements decision-making at inter-iteration time. This paper presents a Grounded Theory study on agile requirements prioritization methods to yield a conceptual model for understanding the inter-iteration prioritization process in terms of inputs and outcomes. The latter is derived by using qualitative empirical data, published earlier by other authors. Such a conceptual model makes explicit the concepts that are used tacitly in different agile requirements prioritization methods and can be used for structuring future empirical investigations about this topic. Keywords - Agile development, requirements prior...