Years ago, there was never any dispute: when you listed a bunch of things in a sentence and finished with the word 'and ________.', there should always have been a comma before the 'and', i.e. "I have lived in France, Germany, Italy, and China."
The modern grammarians (is that even a word, haha) seem to think that the final comma should be omitted because they claim it is redundant. They claim that without the comma, everything should be adequately clear, for example: "I have lived in France, Germany, Italy and China." Is that really clear? I beg to differ, and for two reasons.
First, the comma's use is not just as a separator of things; it is also used as a pause device. Without the last comma, that sentence reads: "I have lived in France (pause) Germany (pause) Italy and China (said quickly together)." That's not correct at all and we all know it. It should read: "I have lived in France (pause) Germany (pause) Italy (pause) and China." The ONLY way to include that final pause is with the comma: "I have lived in France, Germany, Italy, and China."
Second, without the comma, the meaning IS different. For example, "I like to eat pizza, sandwiches, fish and french fries." Come on people: without the final comma, we have no idea what this person means! Does the person like to eat fish and french fries together, or fish as a separate meal and french fries as a separate meal? Returning to the "Italy and China" example, does this mean that the person somehow lived in Italy and China at the same time, i.e. one month in Italy, and then one month in China, back and forth, for a year, living in both places at the same time because of work related conditions, or does it mean that Italy is a separate entity during a different time, and that China is a separate entity during a different time? Without the final comma, we simply do not know.
The bottom line is that you NEED to use that final comma. Screw the modern usage: it's incorrect. -Monroe