The other night I was out with Jason and we were having a discussion about quarterbacks. I made a comment about how I think defensive backs will eventually benefit from this new passing heavy league. My idea was that if there more passes being thrown, then it should make sense that there will be more interceptions. Jason argued with me and feels that it is a horrible time for defensive backs.
I figured (and I think towards the end of a very long rant that Jason agreed with me) that if QBs are throwing way more passes and the rate of interceptions stays relatively the same over time, that there should be more total interceptions. My reasoning was that if you looked back at the old days, there were less passes thrown, but aside from a few outliers, interception numbers would probably be pretty low as well.
I was completely wrong. I am actually shocked by what I found. Here is the data: INT is interceptions, the next column is interceptions per team per game, the next one is pass attempts, after that we have pass attempts per team per game, and last we have the percentage of passes thrown for interception (or interception per attempt).
| Year | INT | INT/Tm/Gm | Pass Attempts | PA/Tm/Gm | Int/Attempt |
| 2011 | 506 | 0.9882 | 17410 | 34.0039 | 2.9064% |
| 2010 | 511 | 0.9980 | 17269 | 33.7285 | 2.9591% |
| 2009 | 525 | 1.0254 | 17033 | 33.2676 | 3.0823% |
| 2008 | 465 | 0.9082 | 16526 | 32.2773 | 2.8137% |
| 2007 | 720 | 1.4063 | 17045 | 33.2910 | 4.2241% |
| 2006 | 520 | 1.0156 | 16389 | 32.0098 | 3.1729% |
| 2005 | 506 | 0.9883 | 16464 | 32.1563 | 3.0734% |
| 2004 | 524 | 1.0234 | 16354 | 31.9414 | 3.2041% |
| 2003 | 538 | 1.0508 | 16493 | 32.2129 | 3.2620% |
| 2002 | 528 | 1.0313 | 17292 | 33.7734 | 3.0534% |
| 2001 | 545 | 1.0988 | 16181 | 32.6230 | 3.3681% |
| 2000 | 634 | 1.2782 | 16322 | 32.9073 | 3.8843% |
| 1999 | 562 | 1.1331 | 16760 | 33.7903 | 3.3532% |
| 1998 | 509 | 1.0604 | 15489 | 32.2688 | 3.2862% |
| 1997 | 479 | 0.9979 | 15729 | 32.7688 | 3.0453% |
| 1996 | 542 | 1.1292 | 15966 | 33.2625 | 3.3947% |
| 1995 | 512 | 1.0667 | 16699 | 34.7896 | 3.0661% |
| 1994 | 474 | 1.0580 | 15056 | 33.6071 | 3.1482% |
| 1993 | 469 | 1.0469 | 14414 | 32.1741 | 3.2538% |
| 1992 | 519 | 1.1585 | 13408 | 29.9286 | 3.8708% |
| 1991 | 488 | 1.0893 | 13950 | 31.1384 | 3.4982% |
| 1990 | 480 | 1.0714 | 13516 | 30.1696 | 3.5513% |
| 1989 | 559 | 1.2478 | 14338 | 32.0045 | 3.8987% |
| 1988 | 553 | 1.2344 | 14131 | 31.5424 | 3.9134% |
| 1987 | 540 | 1.2054 | 13491 | 30.1138 | 4.0027% |
| 1986 | 581 | 1.2969 | 14469 | 32.2969 | 4.0155% |
| 1985 | 602 | 1.3438 | 14423 | 32.1942 | 4.1739% |
| 1984 | 584 | 1.3036 | 14325 | 31.9754 | 4.0768% |
| 1983 | 620 | 1.3839 | 14047 | 31.3549 | 4.4138% |
| 1982 | 349 | 1.3849 | 7933 | 31.4802 | 4.3993% |
| 1981 | 609 | 1.3594 | 14180 | 31.6518 | 4.2948% |
| 1980 | 627 | 1.3996 | 13705 | 30.5915 | 4.5750% |
| 1979 | 597 | 1.3326 | 12979 | 28.9710 | 4.5997% |
| 1978 | 639 | 1.4263 | 11829 | 26.4040 | 5.4020% |
| 1977 | 562 | 1.4337 | 9786 | 24.9643 | 5.7429% |
| 1976 | 497 | 1.2679 | 10260 | 26.1735 | 4.8441% |
| 1975 | 533 | 1.4643 | 9973 | 27.3984 | 5.3444% |
| 1974 | 500 | 1.3736 | 9609 | 26.3984 | 5.2035% |
| 1973 | 470 | 1.2912 | 8845 | 24.2995 | 5.3137% |
| 1972 | 480 | 1.3187 | 9011 | 24.7555 | 5.3268% |
| 1971 | 544 | 1.4945 | 9412 | 25.8571 | 5.7799% |
| 1970 | 510 | 1.4011 | 9796 | 26.9121 | 5.2062% |
| 1969 | 544 | 1.4945 | 10377 | 28.5082 | 5.2424% |
| 1968 | 554 | 1.5220 | 10034 | 27.5659 | 5.5212% |
| 1967 | 593 | 1.6943 | 10329 | 29.5114 | 5.7411% |
| 1966 | 535 | 1.5923 | 10090 | 30.0298 | 5.3023% |
| 1965 | 480 | 1.5584 | 9059 | 29.4123 | 5.2986% |
| 1964 | 501 | 1.6266 | 9187 | 29.8279 | 5.4534% |
| 1963 | 514 | 1.6688 | 8954 | 29.0714 | 5.7405% |
| 1962 | 567 | 1.8409 | 8812 | 28.6104 | 6.4344% |
| 1961 | 564 | 1.8312 | 8922 | 28.9675 | 6.3215% |
| 1960 | 493 | 1.8396 | 7813 | 29.1530 | 6.3100% |
| 1959 | 221 | 1.5347 | 3714 | 25.7917 | 5.9505% |
| 1958 | 243 | 1.6874 | 3951 | 27.4375 | 6.1503% |
| 1957 | 231 | 1.6042 | 3339 | 23.1875 | 6.9182% |
| 1956 | 240 | 1.6667 | 3282 | 22.7917 | 7.3126% |
| 1955 | 258 | 1.7917 | 3820 | 26.5278 | 6.7539% |
| 1954 | 294 | 2.0417 | 4232 | 29.3889 | 6.9471% |
| 1953 | 306 | 2.1250 | 4267 | 29.6319 | 7.1713% |
| 1952 | 297 | 2.0625 | 4024 | 27.9444 | 7.3807% |
| 1951 | 288 | 2.0000 | 3881 | 26.9514 | 7.4208% |
| 1950 | 343 | 2.1987 | 4307 | 27.6090 | 7.9638% |
I realize it looks like a lot to digest, so I was nice and made some graphs.
A few quick notes: 1982 was a shortened season, only nine games were played. From 2011-2002 there were 32 teams that played 16 games. From 2001-1999 there were 31 teams. 1998-1995 30 teams. 1994-1978 28 teams. 1977-1976 28 teams playing 14 games. 1975-1970 26 teams playing 14 games. 1969-1960 was the AFL-NFL times (I had to combine the numbers, the majority of the time they both played 14 games, except in 1960 when the NFL only played 12 games). From 1959-1951 there were 12 teams playing 12 games and in 1950 there were 13 teams that played 12 games.
Here is the interesting thing, the number interceptions has stayed pretty steady since the 1960s. In fact, as the number of attempts increases over time, the rate of interceptions decreases. To me that seems pretty crazy, but I guess it should make sense if you take into consideration that coaches must know what they are doing. I mean, if all these QBs were pretty crappy, they probably would want them to continuing throwing less. Also, there are the rule changes to take into consideration. I am not about to go that deep into this.
I am shocked that coaches passed at all in the 1950s, teams were averaging two interceptions per game and there was almost an 8% chance of an attempt being picked off.
I guess being a defensive back in this era must really suck.
