Which foal crop year was the last to produce multiple Horse of the Year winners?

Which foal crop year was the last to produce multiple Horse of the Year winners?

Which foal crop year was the last to produce multiple Horse of the Year winners? [561 votes total]
2007 (128)	23%
2006 (124)	22%
2005 (139)	25%
2004 (117)	21%
Other (53)	9%