It is a pure coincidence but I just wrote a lengthy article on my blog about teaching students about critical moves which makes them timetrouble-addicts: http://schaken-brabo.blogspot.com/2013/07/mijn-mooiste-zet.html

To summarize, the concept of critical moves has 2 serious defects:
1) There is no way to identify for sure in advance what is a critical move. This uncertainty makes people search for things which aren't there so spending too much time on lots of moves with little to no extra value. This could be regarded as P2 in GeneM question.
2) Even if we do recognize some positions which are critical then still nobody teaches us what exactly is a reasonable time spent. There exist no guidelines so some players just don't realise when they should move on. This can clearly be regarded as P1 in GeneM question.

Changing bad habits (of which being a timetrouble-addict is certainly one) is very difficult so i prefer to prevent. As teacher we can do a lot of prevention by not teaching the concept of critical moves but teaching a more even spread timeconsumption. 

So what to do if you have become already a timetrouble-addict.
1) Write down during the game, the used time after each move or every 5 moves. It gives a certain level of control.
2) Place in advance some intermediate timecontrols for yourself which you want to achieve as a minimum. E.g. 16 moves in 1 hour if the timecontrol is 2 hours for 40 moves
3) Learn to live with the timetrouble and practice a lot of blitz.

Last addition I want to make on the interesting aspect of timetrouble. Once in a while being in timetrouble isn't necessary a bad thing. It means that you are trying to spend well your allotted time and then it can happen due to an exceptional complex game that the usual margin wasn't sufficient. Difficult to put a % on it but I would say 1 out of 10 games being in timetrouble (average less than 1 minute left per move) is still acceptable.

I have to confess that I am a member of the "P1 club" (admitting you have a problem is the first step toward recovery!)  Usually I will lose track of time as I ponder an interesting / complicated position and consume more time than I realize.   Easily corrected but it still happens on occasion!

If I get into time trouble (which doesn't happen too often anymore), it is almost always because of P2. And from my experience, that usually applies to my opponents as well.  The few times when P1 is the explanation, it is usually because the position really was complicated and demanded a lot of time (but maybe not as much as I, or my opponent, actually spent).

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During the first segment of a typical tournament time control...
Time trouble can be caused by either...

P1. Using way too much time on a few moves; or
P2. Using a little too much time on a lot of moves.

** Which of these two causes leads more games into time trouble, P1 or P2? And can the ratio of affected games be quantified (with mere estimates)?

Intuition from players experienced in tournament play is one usable source of answers/info.
Any hard data would also be great.

When I browse through Jon Speelman's Best Games book, wherein he reports time used per move(!), it seems that P2 is far more common than P1. P2 is also my personal experience.

Thanks.
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