You asked for it, you got it. The funny thing is, I was just thinking about this a week or so ago and hoping I could find the file.
The Chiefs' stock index currently stands at -17.26. This is a notable increase from -22.42 at the end of 2009, which was one loss from being in the bottom ten indexes in Chiefs history (all of which had occurred between Week 9 of 1988 and Week 10 of 1989).
When Todd Haley took over the team, the index was at -16.60, so Todd is currently still negative for his career, but that'll happen when you go 4-12 your first year. In looking at the graph, you can see that we have apparently hit a floor in the market, so I would recommend buying Chiefs stock as a long-term buy.
Here's a graph of how the various Chiefs coaches have fared. We can see that only three coaches have produced a positive change in the index: Schottenheimer with an enormous gain, Stram with a strong gain, and Mackovic eked out a minor gain.
Herm presided over the largest drop in franchise history, at almost 22 points. Wiggin was somewhat equivalent, dropping 18 points in fewer games. (Bettis is an outlier considering he coached only 7 games.) Interestingly, though, Wiggin (and Bettis) took over a team that was already in free fall - Stram's teams had dropped 14 points between the Christmas 1971 game and Stram's departure. Wiggin and Bettis merely continued that trend until Levy began pulling out of the dive and Mackovic got the nose turned upward again. The Gansz thing was a failed experiment, producing equivalent results to Herm, more or less, before the Space Shuttle Schottenheimer launched.
As of this point, we can view coaches quite clearly in one of three camps:
Successes - Schottenheimer, Stram
Mediocres - Vermeil, Mackovic, Levy, Cunningham (though Cunningham is pushing the bottom edge)
Disasters - Wiggin, Bettis, Gansz, Edwards
Haley has proven (to date) that he's not in the first camp, and he's arcing upward.
Code:
Start Finish Games PPG Change
Stram 0 16.4706 218 0.08 16.5
Wiggin 16.4706 -1.4429 35 -0.51 -17.9
Bettis -1.4429 -7.2554 7 -0.83 -5.8
Levy -7.2554 -13.9729 73 -0.09 -6.7
Mackovic -13.9729 -13.1761 65 0.01 0.8
Gansz -13.1761 -23.3491 31 -0.33 -10.2
Schottenheimer -23.3491 10.5904 170 0.20 33.9
Cunningham 10.5904 5.4264 32 -0.16 -5.2
Vermeil 5.4264 4.9787 81 -0.01 -0.4
Edwards 4.9787 -16.5967 49 -0.44 -21.6
Haley -16.5967 -17.2639 27 -0.02 -0.7
And you want to hear something else interesting? Haley has produced the second-best start to a coaching career in Chiefs' history when you consider index change. While he's still slightly negative, every coach except Marty was more negative, even Hank Stram.
Index Changes in First 27 Games
Schottenheimer = +8.5
Haley = -0.7
Mackovic = -2.0
Cunningham = -2.8
Stram = -3.0
Edwards = -3.2
Bettis = -5.8 (7 games only)
Vermeil = -6.3
Gansz = -8.0
Levy = -8.8
Wiggin = -12.8