Why is it not surprising to find that the risk premium on the world market portfolio is

Question:

Why is it not surprising to find that the risk premium on the world market is lower than the domestic risk premium?
Portfolio
A portfolio is a grouping of financial assets such as stocks, bonds, commodities, currencies and cash equivalents, as well as their fund counterparts, including mutual, exchange-traded and closed funds. A portfolio can also consist of non-publicly...