Contributing factors to historical increase in trading volume
Prior to 1975, commissions for trading stock on the NYSE were fixed at 1% of the amount of the trade.  In 1975, the SEC made fixed commission rates illegal, giving rise to discount brokers offering much reduced commission rates.  Simultaneously, Electronic Communications Networks (ECNs) gained market share as alternative venues for executing trades.  The increased competition led to further declines in commissions.  Finally, as technology was widely adopted on Wall Street and human beings were largely taken out of the order execution process, commissions fell further.  This had the effect of both drawing in new participants and increasing the rate of transactions of the existing participants (see Day Trading, which was largely unheard of prior to the technology revolution of the 1990s).  Most recently, the exchanges themselves have shifted their business model to depend on high frequency traders, and the proportion of trades accounted for by HFT firms ballooned from under 10% in the early 2000s to over 50% today. It's not primarily more people investing. In the 1980s stock exchanges went from open outcry trading floors where all trades involved actually exchanging pieces of paper to electronic trading. Once that happened, it wasn't long before most trades were executed by computer programs rather than human beings, turning stocks over rapidly for very short-term profits rather than long-term investment, greatly increasing  the number of trades (and also increasing liquidity for the actual investors; it's by no means all bad).
You can't tell for sure.  If there was such a technique then everyone would use it and the price would instantly change to reflect the future price value. However, trade volume does say something.  If you have a lemonade stand and offer a large glass of ice cold lemonade for 1c on a hot summer day I'm pretty sure you'll have high trading volume.  If you offer it for $5000 the trading volume is going to be around zero. Since the supply of lemonade is presumably limited at some point dropping the price further isn't going to increase the number of transactions.   Trade volumes reflect to some degree the difference of valuations between buyers and sellers and the supply and demand.  It's another piece of information that you can try looking at and interpreting.  If you can be more successful at this than the majority of others on the market (not very likely) you may get a small edge.  I'm willing to bet that high frequency trading algorithms factor volume into their trading decisions among multiple other factors. The shift to trading at the close began in 2008. Traders did not want to be caught off guard by surprise news and there was a lot of volatility during the financial crisis, so they would close their position in the evening. Thats how it began. There are two reasons why it sticks around. First, there has been an increase usage of index funds or passive funds. These funds tend to update their positions at the end of the day. From the WSJ: Another factor behind the shift has been the proliferation of passively managed investments, such as index funds. These funds aim to mimic an index, like the S&P 500, by owning the shares that comprise it. Index funds don’t trade as often as active investors, but when they do, it is typically near the market close, traders say. That is because buying or selling a stock at its closing price better aligns their performance with the index they are trying to emulate. The second reason is simply that volume attracts volume. As a result of whats mentioned above, you have a shift to end of day trading, and the corrolary to that is that there is a liquidity shortage from 10am to 3pm. Thus, if you want to buy or sell a stock, but there are few buyers or sellers around, you will significant move the price when you enter your order. Obviously this does not affect retail traders, but imagine hedge funds entering or closing a billion dollar position. It can make a huge impact on price. And one way to mitigate that is to wait until there are more market participants to take the other end of your trade, just as at the end of the day. So this is a self-reinforcing trend that has begun in the markets and will likely stick around. http://www.wsj.com/articles/traders-pile-in-at-the-close-1432768080 The key two things to consider when looking at similar/identical ETFs is the typical (or 'indicative') spread, and the trading volume and size of the ETF. Just like regular stocks, thinly traded ETF's often have quite large spreads between buy and sell: in the 1.5-2%+ range in some cases. This is a huge drain if you make a lot of transactions and can easily be a much larger concern than a relatively trivial difference in ongoing charges depending on your exact expected trading frequency. Poor spreads are also generally related to a lack of liquidity, and illiquid assets are usually the first to become heavily disconnected from the underlying in cases where the authorized participants (APs) face issues. In general with stock ETFs that trade very liquid markets this has historically not been much of an issue, as the creation/redemption mechanism on these types of assets is pretty robust: it's consequences on typical spread is much more important for the average retail investor. On point #3, no, this would create an arbitrage which an authorized participant would quickly take advantage of. Worth reading up about the creation and redemption mechanism (here is a good place to start) to understand the exact way this happens in ETFs as it's very key to how they work. I hovered over the label for trading volume and the following message popped up: Volume / average volume  Volume is the number of shares traded on the   latest trading day. The average volume is measured over 30 days. "There are stocks that have held 100% of the exact same trend (bull or bear) on a date or date range for years. While  history of course doesn't guarantee that the trend will hold for the current year, that fact itself is distinct from the question of whether history is an *indicator* worth building a thesis off of.  The problem is if and when someone thinks ""indicator"" is equivalent to ""definitive answer"".   Answer 2: A dozen big algo traders have disproven this notion.  Answer 3: Price is not only price action itself. It's calendar, evens, binaries, cyclical psychology, etc." Not sure where you got the 296 crores figure. The data on the sheet shows activity by category of investors. In the end NET of all BUY and SELL across all categories will always be Zero. It has no bearing on whether the stock market goes up or goes down. If you compare only activity by certain category, say FII then there could be more SELL compared to BUY or vice-versa. That's a great article. It covered the viewpoints of the exchanges and high frequency traders in more depth than most of the other articles I've read. The balance between the volume HFT provides an exchange versus the resources and strain they put on exchanges is a precarious situation. Historical volatility of a stock is going to be based on past performance, basically its current trend.  That can be useful, but really is no indication of how it will perform in the future.  Especially with a big swing in the market. Now if you're talking about implied volatility (IV) of an options contract, that's a little different.  IV is derived from an option’s price and shows what the market “implies” about the stock’s volatility in the future. Thus it is based on the actions of active traders and market makers.  So, it gives you a bit more insight into what's going on, but at times has less to do with fundamentals. I guess a good way to think of IV based on options contracts is as an educated opinion, of the market as a whole, with regards to how much that stock could likely move over a period of time (options expiration). Also note that IV represents the potential for a stock to move, but it does not forecast direction. I don't know of any studies off the top of my head, but I'm sure there have been plenty.