How to Weed a collection according to me(ad)

Are you an evolutionary,
or are you a revolutionary,
or are you a simple sane weeder?

An evolutionary weeder would follow
what the newest evolution or trend in library science and
would build on the immediate and take most of the new and
emphasize the modern look with minimalistic view of the shelves.
Half empty means ... maybe people are borrowing books more.
But it does not necessarily contain the whole truth and the patrons
(customers) like the library to be a cozy place where they can hide
in the stacks.

A revolutionary weeder would take all the old dingy stuff
and not keep anything that was over five years old.

A simple sane weeder would do a little bit of both, and keep the
shelves as full as comfortably can be. If space was not issue
a sane person would have a storage for some of the books
that a modern library should have - all the classics and some
seasonal changes, in an ideal world. A sane weeder would get the
new shelves to circulate more by reducing the time the books spend there
to 4 months and see if that made a difference.
If you weed you have to leave some old, some newer, and some for each
segment, the very popular, and the very eclectic, some in different format,
but not always rely on the newer formats - because the book has been around for
quite some time, and we are currently seeing a turnover from tapes to dvds.
Also conserve good classical music, even though the cases look terrible and a
they have a low circulation. This theory follows the sane weeder's philosophy,
namely that one day an eclectic patron (customer) comes in looking for the opera
which we should have, but do not!