Bull markets are fueled by sector and industry group rotation. Throughout the bull market since 2009, we’ve seen each of the key aggressive sectors take their turn leading on a relative basis. Within each sector, we also see relative leadership and weakness among industry groups. For example, over the past month, aerospace stocks ($DJUSAS) have performed extremely well. In fact, the DJUSAS is one of only two industry groups in the sector that have moved higher and its 4.17% gain over the past month easily beats defense stocks ($DJUSDN).