Principally, the weighting factor is developed from the current flow and critical flow. For this study, the current flows refer to the 2011 as the base year situation, corresponding to last year of the 5- year term of the recent Tenth National Economic and Social Development Plan (2007e2011) published by the National Eco- nomic and Social Development Board (NESDB, 2006). The official historical data from reliable and publicly available sources and related studies are extracted to use for current flows. Nevertheless,
for some data which cannot be directly used as current flow, different techniques have to be adopted. For instance, extrapolating to base year in case of no record in corresponding year, aggregating data from many sources as a flow, and using sensible assumptions to complete the calculation of flows. The critical annual flows correspond to policy objectives which reflect targets to be achieved within 5e20 years as midterm goals; they depend on the political motivation of each aspect. These are pinned on various years depending on the respective policy target to be considered in the circumstance of both Thailand context and global perspective. Thailand is not as developed as the OECD countries, so the inter- national mandatory measures to reduce environmental impacts such as GHGs emission reduction are not fully adopted yet. How- ever, in accordance of the precautionary principle and conservative perspective, this study has to set the target stricter than the current ones or at least equivalent to the current status with the assump- tion of no further increasing of impacts.