From Knitting with Balls:
Bootcut jeans made their comeback in the late 1990’s. The slits in the cuff were all about allowing your jeans to fit easily over your boots without making anything look too tight or uncomfortable. The Bootcut Sweater offers the same benefits of the pant - offering deep slits in the waist cuff, sleeves, and collar. Based on Elizabeth Zimmerman’s Percentage System, the sweater fits sungly over your torso and arms, and leaves a bit of extra fabric at all the right junctures to ensure a great fit.