To get a idea of the gap between the number of known protein sequences and known protein
structures look up how many entries there are in SwissProt and how many in the PDB.
Aug 2016: Swp >551K; PDB > 117K). The past few years, though, PDB seems to be growing
much faster! At swissProt most time is nowadays spend on improving the data they have
instead of growing the amount of data. The PDB was growing exponentially for many years but
these days the growth seems to be a steady 10K entries per year.