Using a comma after the last word in a list—before you write the word “and”—may seem unnecessary or even incorrect. But as this post explains it can make your writing much more clear. One you start doing it you will see how much it helps your own writing.
If you want to see how much difference a serial comma can make to the meaning of a sentence see this article. You could say it makes 13 million dollars worth of difference! http://www.smithsonianmag.com/smart-news/missing-oxford-comma-just-changed-course-court-case-180962551/