International institutions such as the UN and World Bank adopted a threshold of 1m in the 1970s. Even smaller thresholds have been proposed by some specialists. An important concern with any threshold is the problem of exclusion at the margin - the 'tyranny of round numbers'. A significant number of small states are SIDS, but this excludes an important group of small non-island LDCs. From an economic perspective, the characteristics of SIDS are very similar to those of small states in general.
Most economic issues are common to both.
Limited resource base, including labour. Narrow output and export structures. Structural openness to trade. Vulnerability - economic, political and environmental. The empirical results of the impact of small size on growth are generally inconclusive in spite of the sub-optimality thesis.