Investors can diversify their portfolios internationally by buying foreign stocks directly or investing in domestic companies that invest abroad. Taxes and capital controls affect how investors choose between these options. A study on investments in the US from ten countries in the 1980s found that tax policies did not have a significant impact on the choice of investment method. This is because tax rules adjust to prevent large-scale foreign investments. As global markets become more integrated and capital controls relax, tax distortions affecting international investments are expected to decrease.