One of the simplest ways to improve your effectiveness is to know the pecking order of persuasion. I wrote a post on Sources of Insight about how character trumps emotion trumps logic. This is a pretty important piece of information, considering it impacts how well you influence your peers, your kids, your manager, your stakeholders or anyone, really.
To bottom line it, if your arguments based on data aren't working, consider that if you win the heart, the mind follows, and that who you have on board can make all the difference in your success. Change your approach and you'll be surprised by the results. One simple thing you can do is use more metaphors to make your points. Visual words stick more and they help bring some emotion to the table. Choose carefully, of course.