Another Investment Fallacy

There's an oft repeated saw about 80% of any stocks movement is the market and sector.
Think about that for a moment. Then remember that the 'market' and 'sector' are simply aggregates of these individual stocks. Yes, the economy and the industry are reflected in those.....

It's like saying that 80% of a stocks price is the 50 day moving average. It's much easier to see why that's not quite true even if the correlations would suggest that.
The average is derived from price, not the other way around, and the same applies to the market and sector.

Noodle that one over for a bit and see if it resonates.