STORM2K

I have been looking through hurricane formation dates, and I noticed that post-season Atlantic activity (activity continuing after November 30) was fairly common until recently. Recent examples include Nicole (1998), Olga (2001), Odette (2003), Peter (2003), Otto (2004), Epsilon (2005), Zeta (2005), Olga (2007), and AL142013 (2013). In the 1980s, there was Lili (1984) and Karen (1989). Recently, there has been no post-season activity in the Atlantic. What happened? Were the 2000s anomalous in this regard, or is there something going on that is preventing the hurricane season from continuing after November 30 that is present now but was not present back then?