vim plugin question

[billy61]

I have a question regarding vim.
I know to install vim scripts, I can use ~/.vim/plugin/ to install the plugins for one user, but what if i want to install them system-wide? i use the /etc/vim/vimrc (or /usr/share/vim/vimrc) for my vimrc file, what is the equivalent folder to that for installing plugins?
/usr/share/vim/addons/plugin/ looks to be promising, but I want to make sure before I install a bunch of stuff.

Thanks!