Recession busters - Why three slippers makes a pair

At our last meeting we all started knitting our slipper socks. The pattern was for about a size 7 foot. So I added four more rows for the length of my foot. Then I got on with the knitting. Feeling very industrious I even took the knitting to rugby on Saturday. Ball of wool in my pocket and my kneedling clicking (figuratively only) I gaily finished the second slipper. Only to discover that in my haste and pride that it would get done, I had forgotten about the extra rows and my second one was very tight. So the third one was knitted. Hence it has taken me three attempts to make a pair. I crocheted around the top and it rolled a bit and am very happy with the results. My boys are both saying they want a pair, I think I will be able to shrink that pattern.