Karthik has explained beautifully here http://zerodha.com/varsity/chapter/volumes/
So what does an increase in price, associated by decreasing volumes indicate?
- It means the price is increasing because of a small retail participation and not really influential buying. Hence you need to be cautious as this could be a possible bull trap.
So how would you infer a decline in price and a decline in volume?
- It means the price is decreasing because of small retail participation, and not really influential (read as smart money) selling. Hence you need to be cautions as this could be a possible bear trap.