there is a table with all the exchange rate on the wiki, last of the page
http://en.wikipedia.org/wiki/Japanese_yen
The conversion rate has halved since then, however I don't know what could be guessed from that since in the 1986 shows the conversion from the yen of that time with the dollars of
that time. You can't understand if the change happened because the yen gained value or the dollar lost value.
EDIT: yes that's 20 billions not 200