How should one change the width of scrollbar?

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http://unix.stackexchange.com – I started using Linux Mint 13 Mate a few days ago and I can't find anyway to change the width of my scrollbar, no matter it is firefox, chrome or File Manager. I tried to search google with "Linux Mint 13 scrollbar size" or "Linux scrollbar size" as keywords but the result isn't useful. I looked up all the option in Control Center and found nothing so I doubt they have a option in Linux Mint 13. Actually it is quite a failure although they claim Linux Mint is user friendly. If anyone knows which linux distro has this option please tell me. Thanks. (HowTos)