A Primer on Quantitative Strategy Development¶
Some definitions¶

Systematic Trading
: Trading decisions in a methodical way defining trading goals, risk controls and rules 
Quantitative Trading
: Trading signal generation based on quantitative analysis 
Algorithmic Trading
: Execution of trades using automated preprogrammed trading instructions 
HiFrequency Trading
: Algorithmic trading characterized by high speed, high turnover rates and high ordertotrade ratios
What is a trading strategy¶
Strategy
: A set of rules or a welldefined algorithm to choose an
action from the set of all possible actions in any state of a game.
Trading Strategy
: Strategy (above). The game is stochastic
(state transitions are probabilistic), massively multiplayer and
potentially long running.
From a practical point of view, a trading strategy is nothing but an algorithm that takes in as input a set of data (like asset prices, state of the economy, fundamental ratios etc.) that captures the relevant subset of the current state of the world, and generates a series of orders.
The strategy spectrum¶
Trading strategies are diverse. But one way to look at it is from the point of view of trading style and the underlying factor that guides the profit or loss of the strategy. See below:
Here we capture the trading styles in the vertical axis and the profit
driver on the horizontal axis. Different styles try to capture the same
underlying driver in different manner. For example, value investing
for a fundamental investor, or swing trading
of a technical trader or
statistical arbitrage
of a quant trader  all focus on the same
underlying driver  mean reversion
. For the value investors, it is
deviation from the fair price
. For technical traders it is from the
technical levels
or support and resistance
. For quant traders it
is from the modeled behaviour of relative price of two assets.
If you look closely, you will notice that almost all strategies can be adapted for a systematic approach.
Fundamental vs quant trading¶
Tale of two styles¶
Let's understand the difference between fundamental vs. quantitative approach of investing through an example:
Asset manager A is a discretionary manager and follows 10 stocks diligently. Asset manager B is a systematic manager and has enough computational power to track 500 stocks. Investors seek outperformance and certainty.
Question #1
: What is thehit ratio
for A to achieve outperformance in at least 50% (total 5 stocks) of his portfolio with at least 95% probability?Question #2
: What is thehit ratio
for B to achieve outperformance in at least 50% (total 250 stocks) of his portfolio with at least 95% probability?
Solution: Let the success rate (or hit ratio
) be p. Total
required success n, total trial N. Probability of n success out
of N trials follows the binomial distribution:
Probability of at least n success (n=5 for A, n=250 for B):
We need to solve for p for A and B, such that P is 0.95 in both cases. The result, once plotted, looks like below:
We see that the asking skill level
or hit ratio
for B is much lower
than A. B has to be right only around 55% of times, whereas for A, the
accuracy needs to be more than 80%  which is no mean feat! This brings
us to the most important concept of investment  the fundamental
principle.
Fundamental law of active management¶
The fundamental law of active management states^{1}:
Information Ratio (IR)
: Measure of success – risk adjusted returns over the chosen benchmarkInformation Coefficient (IC)
:Linear relationship between predicted asset returns and realized returns, usually in the range of 0 to 1 (unlike correlation range of 1 to 1, as you can always short the prediction of someone who is consistently wrong!!).Number of Bets (N)
: Number of independent bets that can be made in a given timeframe.Transfer Coefficient (TC)
: The linear relationship between predicted asset returns and actual trading positions. This ideally should be one, but can be lower (risk limits, capital limit, bandwidth problem due to work overload etc.)
This makes it clear the essential edge in quantitative trading  N. As a fundamental investor our edge comes from deep research in to the underlying securities. This automatically restricts the number of stocks we can cover. In quant trading, we can observe a very large number of trading instruments systematically for trading opportunities.
It does not really mean one style is better compared to another. While the fundamental trader covers only a few stocks and requires a much higher level of skills and subjective judgments, the upside are also potentially large (multibaggers!). Quant trading requires a different set of skills and returns are usually more predictable and steady, if based on solid principles.
Systematic strategy design cycle¶
The systematic strategy design cycle looks like below:
The steps consist of the following:

selecting universe
: This is the set of trading instruments that we observe for opportunities. This is usually static (e.g. futures of the index) or systematically defined (e.g. all stocks inS&P500
). It also depends on other factors like geographies, regulations, fund size, liquidity requirements, investment mandates etc. 
signal generation
: This is the step where we continuously observe and compute a quantitative metric on all instruments in our universe. It can be a technical indicator likeRSI
, or a factor likemomentum
or combinations of many such metrics. This defines our potential trading intentions for each of these instruments. 
target portfolio generation
: Based on the step above, and taking in to account our current portfolio and other constraints, we come up with a target position for each instruments (including 0). This is the portfolio we want in our current strategy iteration. 
rebalancing
: This is the step where we translate our target portfolio to actual orders and positions. All order sizing functions, execution strategies etc. sit here. 
improvement
: And finally of course we look at the results of the current iteration and improve our strategy in this continuous cycle.
Systematic strategy design pillars¶
The major pillars of a systematic strategy development are defining
strategy inputs, designing the trading rules, validating the trading
rules, portfolio (meta strategy
) design and risk management.
 Inputs: Input to the strategies can come in many flavours like
 Price/ returns and it’s transformation. Most of the common technical indicators are transformation of price returns2
 Positioning information – volumes and open interest data and participantwise positioning data if available
 Fundamental information –macroeconomic information, company fundamentals
 Nonmarket information: Example twitter sentiments, analysts’ ratings etc.
 Trading Rules/ Logic: Can be either based on trader’s hypothesis
or inferred (learned) from data
 Form hypothesis (e.g. moving average crossover signals change in trends) and test – traditional approach
 Feed data to infer rules (the subject matter of machine learning and artificial intelligence)
 Backtesting and Forwardtesting: A crucial step and often
overlooked step.
 A good platform to guard against biases : datamining bias, survivorship bias, marketimpact modeling, lookahead bias
 Should be flexible, eventdriven (to avoid lookahead bias) and with builtin analytics
 Portfolio Creation/ Optimization: Never go allin with a single
strategy
 Two strategies better than one – if they are uncorrelated (in terms of signals and/ or performance)
 Various methods exists – ensemble, traditional portfolio theory, dynamic portfolio allocation etc.
Risk management in systematic strategy¶
Risk management is an integral part of systematic strategies and plays an important role in each part above. It starts with the inputs. One of biggest issues quant strategies are quality of input data. The input data quality and timeliness are fundamental in building a solid and stable strategy. Second, during the research phase, the major risks are various human conginitive biases (that leads to selective research and biased outcome) and experimental biases (e.g. datamining and overfitting ). One of the major biases during the backtest phase, which happens to be very frequent among beginners, is the look ahead bias. An eventdriven backtesting engine becomes a crucial tool to handle such cases.
Once the strategy is tested and deployed, the risk management switches to controlling the inputs (data quality) and outputs (orders, positions etc.) of the strategy. The key parameters to control are
trading frequency
 how frequently the algorithm is trading vs. expectation. A rogue strategy sending orders too fast is known asmachine gunning
.trading amount
 how large the individual generated orders are, compared to expectation. This avoids thefatfinger
problem.restrictions
 several restrictions can be implemented based on requirements, that keep the strategy under control. This includes restriction on maximum leverage, maximum exposure, maximum position size, maximum number of orders in a given period of time and many otherskill switch
 finally, a systematic strategy should always be built with akill switch
, that enables us to quickly stop the execution in case things go wrong or the strategy behaves unexpectedly.