First off, apolgies for the length of post.
The point I would make (if you'll pardon the pun) is that in that general area there are several points that will achieve a dropping effect. The point you refer to as subclavian can be further broken down into two areas of stimulation in my opinion dependant on where you are in relation to your opponent.
If we take a look at the trapezius and surrounding area from a back view (i.e. with you standing behind your opponent) we can see that two of the best points to use are GB21 & TW15/TW16. These are struck straight down vertical for best results (in my experience anyway). These are pretty much in the centre (back part) of the trapezius muscle midway between shoulder point and join to neck.
From the front and opposite (almost) to the above points is LI17. If you 'draw' a triangle from the tip of the collar bone nearest the throat (ST11 point referred to earlier), follow the collar bone along to the tip of the shoulder you will the base of a triangle. If you then follow the trapezius up to its connection with the sternocleidomastoid muscle then back down to St11 point, you will have now created a triangle. Roughly in the middle if this is the point LI17.
Both the back points and front points discussed above can certainly be grabbed together in a clawing motion and this will certainly drop most people. This really though is not the best way to attack these points.
The best way to attack these points is through a 'sudden and heavy' (heavy being the keyword here) over-stimulation across the top of the trapezius muscle at the same level as the points already mentioned. A strong stimulation at this area will create what is called a 'Brachial Plexus Stun'. If you get a correct hit or press on this area the body has a characteristic motion.
The person attacked will generally exhibit a characteristic 'bounce and plummet' body motion (i.e. they will tense up then lose the ability to stand or do anything) as you create a strong 'motor control dysfunction' (due to the effect on the processing part of the brain - more on this another time if I get chance).
However, to create this effect the strike must generate sufficient penetration through the use of correct body dynamics. If this is done your accuracy doesn't have to be as accurate due to the creation of a 'Fluid Shock Wave' through the surrounding tissues and musculature (ripples in a pond when you throw a stone into it are a good visualisation).
Anyway, my apologies for going slightly off topic but thought it might be of interest to someone. dum de dum
P.S. Stay the heck away from ST9 unless you're in real trouble, too much can go horribly wrong with that point. In a real situation fair enough, in training don't let anyone hit you there. Also, ST11 is a very nice point especially when combined with an opposite side squeeze on the other side of the neck.