Well, I'm not sure "most" is entirely accurate. The Torah, except perhaps
for parts of Genesis, was written in Egypt and the desert before entering
Israel. Several of the prophets wrote from Babylon. Many of the Psalms
were composed while David was 'on the run.'
The bulk of the New Testament was written outside Isreal, since it is mostly
Paul's letters from the road. While the gospels take place in Israel, it
is not clear where they were written down (e.g., Luke may have been traveling
with Paul, and John may have been in exile already).
Of course, that's just the orthodox interpretation. Others believe the
Bible was written by William Shakespeare, who had lots of free time since
Richard Bacon was writing all the plays bearing Will's name...
-- Ernie P.
P.S. Actually, I do think Adam was technically correct, since most of the
history and prophetic books of the OT were written in Israel, so over 50% of
the text in the Bible was arguably written in Israel.