40% of all Bitcoins are owned by just 1000 individuals.
This gives them a disproportionate amount of control over the market as they are able to dump them at anytime.
This is not to mention the high proportion of bitcoins held by miners and exchanges, who may have perverse incentives to ensure that as many people buy up bitcoin as possible and hold it for long enough for the price to rise.
Is there any way to deal with the high degree of centralisation that Bitcoin has?
You can't do anything about it. Probably 1000 people own most of the world wealth too so It is not surprising that something similar is happening with btc. That's called capitalism. And the opposite where everybody shares everything would be communism. If everybody had the same amount of money, either everybody would have Ferrari's or nobody would have any cars. Some people must be poor so some others can be rich. That's how it works.
Well said about the working principle of the world economics. It is impossible to have uniformity with everything. Above quote clearly portrays the reality of the market. Let us assume the 1000 individuals owning the most wealth of the world are the most bitcoins holders. The common public is the nodes, just because of the bitcoins got hold within those 100 people these nodes doesn't stop its functioning. The process keeps running unlike the holding.