the pectorial majoris is a large muscle that encompases the entire chest. However what some forget is that eventhough it is one muscle it connects in many different places. The colar bone and all along the sternum. Were this muscle connects at each different point is were we get the concentration on the different angles of the exercise. Do inclines work your entire chest, yes. Do they hit the clavicular connection to a greater degree in my opinion yes. The squeeze is harder there as the pectorial muscles pull the upper arm towards the center of the upper chest. I know I will probably recieve flames for this but you can look in any anatomy book and see how the pectorial muscles originate and connect to the chest. Not to mention who can tell me they do not feel a tighter squeeze in the upper chest doing inclines and a tighter squeeze in the lower chest doing declines.