When the CLMV countries became members of ASEAN from the mid-1990s, there had already existed economic disparities within and between the six older members. Economic disparity, perceived to be a hindrance to economic integration, grew larger within the enlarged grouping with the admission of the CLMV countries, raising concerns about difficulties arising out of and now transitioning from a two-tiered to three-tier regional structure that includes high, middle, and low incomes countries.