All five steps of lean thinking (Value, Value Stream, Pull, Flow, and Perfection) focus on customer (stakeholder) value. The fundamental purpose of systems (products, and services) in to provide value for stakeholders. Systems engineers are leaders of systems thinking, systems integration, and systems decision-making. Therefore, systems engineers play a critical role of working with stakeholders to identify and measure stakeholder value during the system life cycle to support systems decision making. Lean and system engineering have very common goals. However, in order to achieve these goals, they need to be able to qualitatively and quantitative define stakeholder value. For complex, dynamic, and interdependent systems there are many system functions that create value for multiple stakeholders. System designs must consider conflicting values and objectives of these multiple stakeholders. This presentation illustrates the use of functional analysis and Value-Focused Thinking with multiple objective decision analysis to develop a mathematically sound value model that clearly identifies stakeholder value across the life cycle value stream and measures the potential value of system designs and improvements that can effectively and efficiently increase potential value. The presentation illustrates and advocates the early development of the value model and the use to the value model to assess value trade-offs during the entire system life cycle.