The answer why ES has the largest volume relative to the YM is because the SP500 is used as a legitimate hedge for the index funds based upon the SP500. There are very few index funds based on the Dow, thus less hedging from the players.
Now if you are a daytrader you want to play against the most professionals you can because they are the ones that watch what? Right........they watch the basic setups and trade accordingly. Many new traders will cringe at that last statement because new folks first try to reinvent the wheel and or say the bots control the game. ..
KISS works, stay in the game long enough and you will agree with me. The good news is that kiss works so well that you only need to watch price......NOTHING else. Now that last statement will also inflame some because again many do not understand how simple trading can be if they understand simple TA and what is behind the greed, fear and self preservation of the players in the game. A misunderstanding of the players in the game is what makes trading so difficult, not the price movements.
Volume is not needed at all and the same goes for other indicators, nothing is needed except price alone "IF" one can understand what the players are looking for as price will do what it will do.
Their is a huge myth out there that volume can lead price, it is just that.... a myth. If a trader can understand what formed the support/resistance, etc and other simple TA on the charts he/she should be able to know what said traders will do next as price leaves the chicken tracks on the chart....chicken tracks if understood correctly will put you in the other traders heads...so you will think like them and thus you can plan ahead. ..
Think what the players are doing, think where they will be influenced by the basic human mind when price movements ping the players fear, greed and self preservation instincts. What makes traders react? Right, fear and greed and saving their own ass. Good luck...and remember this....To understand the other players enough to where you feel your intuitive mind is in sync with theirs is going to require a lot of screen time. Experience is where the mental aspect of trading works wonders, you will never hone the skills any other way.
When i first got into trading futures after stocks i was surprised when i read about how long many big shooters said "IT takes a few years".....the truth be known,,,,they are right, the hard part of trading is not the mechanics ....it is the getting inside the heads of others to know what you are doing. Thats when you slice bacon daily. ..
