Is it too hard to demote from a tier?

Data found here: http://www.lolsummoners.com/stats

The quantity of players in the lowest division of the tier from Silver onward (for example: Diamond V) is higher than that of the quantity of players in the highest division of the previous tier (Platinum I) even though the general trend from Silver onward is that the numbers will keep going down for successive divisions.

Also, what is commonly seen in the regional data is that there tends to be 4x more Diamond 5 players than Diamond 4 players in any given region, over 2x more (approaching 3x) Platinum V players than Platinum IV players, and over 2x more (approaching 3x for some of them and above 3x for others) Gold V players than Gold IV players.

I don't play ranked matches and won't be doing so for a long time (I don't have champions and most of the champions I want are expensive), but I'd like people opinions on this. There appears to be an excess of players in the lowest division of tiers from Silver onward.