I dunno, what does $800 B and $500 B have to do in common? Both are investments made by China and Russia into the U.S. homemarket through Fannie Mae and Freddie Mac. That is a whole heck of a lot of (now Treasury backed meaning the U.S. taxpayer) mortgage securities. An astute investor could perhaps discuss how this could be a problem for our monetary system.
That excludes me... :^)