The short answer is yes. The accepted true average has been downsized [this in itself does not mean that adult penes themselves have been shrinking...!] Recent studies have suggested that environmental factors have indeed caused the size of genitalia in male babies to shrink.
The trouble is that most of the actual surveys of penis size are unscientific and unreliable. The Kinsey survey relied on men to report their own numbers honestly and accuratelynever a good idea. (Curiously, that survey found that gay men reported having longer penises than straight mena finding never since replicated.) Since Kinsey's was the first and largest survey, the rounding-up to 6 inches has become the urban myth that has stuck.
The Journal of Urology puts the average penis size at 5.08 inches, and the International Journal of Impotence Research puts it at 5.35 inches.
There have been reports that genitalia in male babies are getting smaller due to environmental factors, such as [SIZE=-1]oestrogen contamination in water supplies; plastics manufacturing by-products; mothers who have given birth after years of taking the birth-control pill and so on. [/SIZE]