Although they’re usually not as orderly as an uptrend, downtrends also tend to move in a step-like or zig-zag fashion. For example, a stock could decline over the course of many days. Then it may retrace part of the loss over the next few days before turning south once more. When this behavior is repeated over time, the downtrend of the chart becomes easier to see. The move downward is the trend itself, with bear rallies or retracements being visible as the counter trend.
It is estimated that more than 75% of stock trades in United States are generated by algorithmic trading or high-frequency trading. The increased use of algorithms and quantitative techniques has led to more competition and smaller profits.[17] Algorithmic trading is used by banks and hedge funds as well as retail traders. Retail traders can choose to buy a commercially available Automated trading systems or to develop their own automatic trading software.

This trading strategy used to be defined as spread trading where you would take profits where small gaps expanded and contracted between the bid and the ask price for a stock. This strategy has now evolved to include technical indicators, support/resistance levels, and volume spikes to make round-trip trades lasting seconds to a few minutes. The basic idea of scalping is to take advantage of market inefficiencies using speed and high trading volume to create quick profits. Click here for more information on scalping.
News provides the majority of opportunities from which day traders capitalize, so it is imperative to be the first to know when something significant happens. The typical trading room contains access to the Dow Jones Newswire, constant coverage of CNBC and other news organizations, and software that constantly analyzes news sources for important stories.  
In addition, in the United States, the Financial Industry Regulatory Authority and SEC further restrict the entry by means of "pattern day trader" amendments. Pattern day trader is a term defined by the SEC to describe any trader who buys and sells a particular security in the same trading day (day trades), and does this four or more times in any five consecutive business day period. A pattern day trader is subject to special rules, the main rule being that in order to engage in pattern day trading in a margin account, the trader must maintain an equity balance of at least $25,000. It is important to note that this requirement is only for day traders using a margin account.[20]
ECN/Level 2 quotes: ECNs, or electronic communication networks, are computer-based systems that display the best available bid and ask quotes from multiple market participants and then automatically match and execute orders. Level 2 is a subscription-based service that provides real-time access to the Nasdaq order book composed of price quotes from market makers registering every Nasdaq-listed and OTC Bulletin Board security. Together, they can give you a sense of orders being executed in real time.
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