Just like the idiom says, to not put all your eggs in one basket, insurance and reinsurance are founded on diversification. Pooling among policyholders, lines of businesses, perils, etc., are typical ways to achieve an adequate level of diversification to lower required capital. However, there are several factors that can act to hamper diversification, even on an international basis: namely the concentration of wealth and population in a few large countries (USA, China), and natural climate phenomena such as El Niño and climate change that both affect many countries.