The transport agencies and Avinor AS have not yet established a joint consensus about what methods shall be used for calculation of net ripple effects in socio-economic analyses. Net ripple effects have during the last few years been subject to considerable attention and they are considered very relevant as a basis for making decision. The objective of the assignment is to develop a method for calculations of net ripple effects that is to the largest possible degree based on professional consensus and agreeable for the transport agencies and Avinor. The method shall be used in analyses that are implemented in connection with the work on the National Transport Plan (NTP) 2022-2033. This means that the method shall be ready for implementation from and including Medio 2018.