To
accurately
compare
numbers,
they must
be
computed
on the
same
basis,
using the
same
definitions
.

If
there are
differences
in
methodology,
you must
recompute
the
numbers
using the
same
methodology
.

Non-comparable
information
is
frequently
provided
by
government.
Definitions
are
changed
for
various
political
reasons.
Often the
methodology
used for
computation
and
comparison
is
obscured.
Numbers
are
computed
on
different
bases from
year to
year to
"spin"
the
numbers.
Comparing
non-comparable
numbers
can be
used to
show that
the
economy is
growing
when it
isn't,
or certain
groups of
people
need more
(or less)
government
aid, or
there
aren't
enough (or
too many)
teachers,
etc.

However,
there is
simply no
way to
compare
numbers
computed
using
different
definitions
as a basis
for the
calculation
. It is
absolutely
essential
to compute
numbers on
the same
basis
before
comparing
them.