Complex sentence: The companies were 50% owned by direct private investors and 50% by all the citizens of Bolivia over the age of 21 and resident in Bolivia, as was the case with the capitalizations of the other four principal state-owned companies.
Split into simpler sentences: The companies were owned 50 percent by direct private investors and 50 percent by all the citizens of Bolivia over the age of 21 and resident in Bolivia. This was also the case with the capitalizations of the other four principal state-owned companies.