I'm not a parent but rather a 19 year old kid at university living at home. I have to do some basic chores, depending on the days I have to cook dinner for myself, etc... . I don't pay the parents as they say I can continue living as long as I'm in classes. Also have to work during the summers full-time as I don't work (parents won't let me) during the normal school year.

Maybe he doesn't feel punishment is right or that the behavior deserves punishment. Also, could be that you are seen to deal the punishment, so why should he? Those are my guesses.

I don't know what your punishment methods are but you could try being harsher if the current ones are having no effect. You may also have to show him that you're not going to put up with his behavior, but when he changes, ease up. The punishments, to me, should be something that makes the person worried or scared, not a little "fine, let's do the punishment then go back to doing whatever". That gets you nowhere and gets him to in a sense, dominate you, because although you dictate the punishment, he'd dictate how it goes. Therefore, he could annoy you and doing that, control you somewhat.