By adding in the latest years storms the entire record average is
raised, even though the same number of storms occurred in yesteryears.
Then by comparing the latest decade to a higher total average, it
reduces the apparent increase in this decades activity. A fair
comparison would be the record from 1851-1995 to 1996-2005 to get the
true picture of how much more severe the weather has gotten this past
decade.

THE BOTTOM LINE:

PERCENTAGE DIFFERENCE 1996-2005 to averages 1851-1995
108% MORE Tropical Storms, 1996-2005
47% MORE Hurricanes Category 1, 1996-2005
29% LESS Hurricanes Category 2, 1996-2005
43% MORE MAJOR Hurricanes Category 3, 1996-2005
80% MORE MAJOR Hurricanes Category 4, 1996-2005
257% MORE MAJOR Hurricanes Category 5, 1996-2005
(Not counting Wilma past TS stage)

====== the math used to compute =========
http://tinyurl.com/bbw92
Archived copy of msg: The Hurricane Record (adapted from HURDAT
1851-2002 with 2003-2005 from
Wikipedia)
Use this URL for reference data these figures were computed from.

http://tinyurl.com/7gpnq
Archived copy of msg: Latest Recomputation of Hurricane Intensification
(inclusion of 2005 data upto TS Wilma)
Correction link for above: http://tinyurl.com/9yvss

COMPARISON 1851-1995 to 1996-2005
For brevity sake, abbreviations are used:
TS = Tropical Storm
C1 = Hurricane Category 1, C2 = Hurricane Category 2

1851-1995 (145 years)
TS : 23=1, 31=2, 24=3, 26=4, 14=5, 8=6, 6=7, 4=8, 1=9, 1=11
23+(31x2=62)+(24x3=72)+(14x5=70)+(8x6=48)+(6x7=42) +(4x8=32)+9+11= 369
Tropical Storms
C1 : 40=1, 38=2, 22=3, 12=4, 8=5, 1=6
40+(38x2=76)+(22x3=66)+(12x4=48)+(8x5=40)+6= 275 Hurricanes Category 1
C2 : 47=1, 36=2, 12=3, 8=4, 2=5
47+(36x2=72)+(12x3=36)+(8x4=32)+(2x5=10)= 197 Hurricanes Category 2
C3 : 46=1, 24=2, 12=3, 3=4, 1=5, 1=6
46+(24x2=48)+(12x3=36)+(3x4=12)+5+6= 153 MAJOR Hurricanes Category 3
C4 : 43=1, 12=2, 3=3
43+(12x2=24)+(3x3=9)= 76 MAJOR Hurricanes Category 4
C5 : 17=1, 2=2
17+(2x2=4)= 21 MAJOR Hurricanes Category 5

1996-2005 (ten years)
TS : 3=4, 2=5, 1=6, 1=7, 1=8, 2=9
(3x4=12)+(2x5=10)+6+7+8+9= 52 Tropical Storms
C1 : 3=1, 3=3, 2=5, 1=6
3+(3x3=9)+(2x5=10)+6= 28 Hurricanes Category 1
C2 : 3=1, 1=3, 1=4
3+3+4= 10 Hurricanes Category 2
C3 : 5=1, 3=2, 1=4
5+(3x2=6)+4= 15 MAJOR Hurricanes Category 3
C4 : 2=1, 4=2, 1=3, 1=5
2+(4x2=8)+3+5= 18 MAJOR Hurricanes Category 4
C5 : 3=1, 1=2
3+2= 5 MAJOR Hurricanes Category 5

1851-1995 (145 years)
369/145 = 2.5 TS per year = 25 per 10-years Tropical Storms
275/145= 1.9 C1 per year = 19 per 10-years Hurricanes Category 1
197/145= 1.4 C2 per year = 14 per 10-years Hurricanes Category 2
153/145= 1.05 C3 per year = 10.5 per 10-years MAJOR Hurricanes Category
3
76/145= 0.52 per year = 5.2 per 10-years MAJOR Hurricanes Category 4
21/145= 0.14 per year = 1.4 per 10-years MAJOR Hurricanes Category 5

1996-2005 (10 years)
52/10= 5.2 per year = 52 per 10-years Tropical Storms
28/10= 2.8 per year = 28 per 10-years Hurricanes Category 1
10/10= 1 per year = 10 per 10-years Hurricanes Category 2
15/10= 1.5 per year = 15 per 10-years MAJOR Hurricanes Category 3
18/10= 1.8 per year = 18 per 10-years MAJOR Hurricanes Category 4
5/10= 0.5 per year = 5 per 10-years MAJOR Hurricanes Category 5

PERCENTAGE DIFFERENCE 1996-2005 to averages 1851-1995
1/25 x 52 = 108% MORE Tropical Storms, 1996-2005
1/19 x 28 = 47% MORE Hurricanes Category 1, 1996-2005
1/14 x 10 = 29% LESS Hurricanes Category 2, 1996-2005
1/10.5 x 15 = 43% MORE MAJOR Hurricanes Category 3, 1996-2005
1/10 x 18 = 80% MORE MAJOR Hurricanes Category 4, 1996-2005
1/1.4 x 5 = 257% MORE MAJOR Hurricanes Category 5, 1996-2005