The first recorded use of long-scale terms ("bymillion" = 10^12, "trimillion" = 10^18) was in 1475. A 1484 article by a French mathematician extended the long scale as far as "nonyllion" (10^54), and this usage became widespread in Europe. The use of the word "milliard" meaning "thousand million" in the long scale dates back to around 1550. In the early 1600s, a few scientists in France and Italy chose to redefine "billion" as 10^9, the first use of the short scale; this usage was later brought to the English colonies in the New World, while England itself retained the long scale. In the 1800s, the US officially adopted the short scale, while France made a partial conversion to the short scale. France then reverted to the long scale in 1961 (after considering the change since 1948), Britain switched to the short scale in 1974, and Italy confirmed use of the long scale in 1994.

In summary, the long scale came first, but the US adopted the short scale; and because of US influence the short scale is now official in most English-speaking countries. The long scale remains in use in most of the rest of Europe as well as other countries whose main languages are European. A few countries, mainly in eastern Europe, use the short scale except that they also use the long-scale term "milliard" to mean 10^9. And much of the Far East uses a completely different system based on myriads.
Source(s):
http://www.economicexpert.com/a/Long:scale.htm
http://en.wikipedia.org/wiki/Long_and_short_scales


Permalink | Report