Before we delve into what Market Internals are, lets ask another question to ourselves - Why does a (Stock Market) Index move?

To understand that we need to move to one level deeper and ask as to - What is an Index?

What is an Index? - An Index is a weighted average value derived from a set of constituent stocks, ie the price of the constituent stocks. So if the prices of the constituent stocks go up the Index which is nothing but an average of those prices would also go up, and the same would happen if the prices of the stocks go down.

In a way we have now answered the question - Why does a (Stock Market) Index move? - An index moves because the prices of the constituent stocks change.

These changes can happen over various time frames. Within a few minutes? Sometimes hours, days, years and so on. But the phenomenon is the same - Prices of Constituent Stocks Change leading to a change in the Index Value.

Now with that sorted, lets move to the concept of Market Internals - Market Internals refers to the data derived from the constituent stocks, which could be used to understand the Index’s structure and strength better.

One way to think of Market Internals is to think of it as Instrument Panels in a Cockpit. If The Aircraft has to fly the way it ought to, all the reading on the instrument clusters need to be within a threshold.

Same is with an Index. If the Index is expected go up then the “Instrument Clusters” ie the Market Internals need to align in a particular way.

Lets take an example -

^NIFTY has 50 Constituents. Their Weight-ages look like this. The top 10 stocks account for close to 60% of the Index, the next 15 add up to 20% more, and the last 25 add up to another 20%.

In other words, being an index with just 50 stocks of which 10 stocks constitute close to 60% of the index makes it a very top heavy index.

This NSE Replica by Equity Master is a nice tool to give you a sense of what they call NIFTY Sensitivity. What it tells us is - For a given change in the price of Stock A how much will the Index Move. Lets look it up for HDFCBANK

For reference lets take the last one on the list HindPetro

HDFCBANK has a 15x more impact on the Index compared to HPCL.

Hope you are with me so far? - We are still exploring what Market Internals are?

Back to where we left.

Lets say you are an Intraday Trader and you expect the market to go from 10600 to 10700 today. A good 100 point move. For such a move to happen? What do you think would happen under the hood? Can HDFC bank be down say by 2% and a few other heavy weights are down or perhaps flat, would we still get a 100 point upside move. As you would guess the chances are quite less.

Like wise what if you see that the top 8 stocks by weightage are all nice and green, trending up - Now what would be the odds of getting that 100 point move? Quite good right.

Lets look at another aspect, what if the trading volumes in the top 10 are quite light compared to its 20 day average? Do you think we would have a trending high range day?

What if the to 10 and the next 15 stocks are going in opposite directions? Do you think we would get a trend day?

I hope you get the drift. Market Internals are these variables or data which are generated by the constituent stocks, analyzing which can help us understand the overall state or health of the market.

If you look at the US Markets esp. NYSE you will see that the exchange broadcasts live Market Internals like NYSE Tick - Which is the number of Stocks Upticking minus the number of stocks Downticking. In lie markets it gives you a sense where in which direction the skew is. This data can be in turn back-tested to identify thresholds of Intraday tops and bottoms. It should not be confused with Advance Decline Indicator which references the Previous Day Close for its calculation. Where as the Tick uses the previous close.

It would look like the one in the image below.

Second, they have something called NYSE Upvol and DownVol, which is broadcasted as two separate values, but many platforms allow you to plot the difference ie Upvol-Downvol. Which tells us which side is volume skewing i.e How much volume is associated with the Upticking stocks vs how much of it is with the Downticking stocks.

Image Courtesy - http://www.traderslaboratory.com/forums/topic/2524-nyse-up-volumeuvoldown-volume-dvol-comparison/

As Intraday Index Traders we in India miss out on this vital informational edge. Not calling it a Holy Grail but nevertheless extremely important to gauge the mood of the market.

As they say what do you do if you cant find what you want? You build one.

In the following weeks we will look at the various Market Internals based Indicators which we have created for our use at NiftyScalper.