commuting to work

18.7 mph average to work today. I've been trying to figure out the reason for the slow down. No long ago I used to average high 18's to 20mph. Lately it's been in the 16's. Is it the bike or maybe the extra 10lbs of ballast I put on over the winter. After adjusting the rear wheel bearing it improved but that extra weight shows most on climbs. No change on the downhills but the climbs are much slower. That 10lbs feels like 100 on long climbs. Guess thats a good reason to be a data freak. It tells you when theres a problem.