I happened to look up my reputation this morning, and it shows this for the "Year" tab:
Note that my reputation for the year is 100 points higher than my total reputation, even though I have only been around for 8 months, so all the months were I could gain any reputation and where I collected total reputation fall into this year. How can that be? I'd also have expected that total reputation has to be as large or larger than reputation from any time period.