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Dynamic Momentum and Contrarian Trading

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Academic paper

Dynamic Momentum and Contrarian Trading

AuthorsVictoria Dobrynskaya

Institute
  • RUNational Research University Higher School of Economics
  • ?School of Finance, HSE University

Strategy in a nutshell

The strategy targets US stocks sorted into deciles based on the previous year’s returns, excluding the most recent month. Under normal conditions, the top decile (“Winners”) is bought and the bottom decile (“Losers”) is sold short, forming a WML (Winner minus Loser) momentum portfolio held for one month. If a market crash occurs—defined as a return more than two standard deviations below the mean—the strategy switches to a contrarian LMW (Losers minus Winners) position for three months before reverting to WML, with monthly value-weighted rebalancing throughout.

Economic rationale

Momentum crashes are partially predictable and tend to follow periods of strong momentum returns, low interest rates, or rebounds after prior losses. These crashes result from the strategy’s reliance on recent performance, which can amplify market downturns. Incorporating a temporary contrarian LMW approach after a significant loss helps mitigate crash risk, potentially turning downturns into profitable opportunities and aligning the portfolio more effectively with prevailing market conditions.

Backtest performance

Annualised return21.74%
Volatility26.74%
Beta0.06
Sharpe ratio0.81
Sortino ratio0.191
Maximum drawdown-39.39%
Win rate53%

Full Python code

import numpy as np
from AlgorithmImports import *
from pandas.core.frame import DataFrame
class DynamicMomentumContrarianTrading(QCAlgorithm):
def Initialize(self):
self.SetStartDate(2000, 1, 1)
self.SetCash(100000)
self.weight:Dict[Symbol, float] = {}

# Monthly price data.
self.data:Dict[Symbol, SymbolData] = {}
self.period:int = 13
self.quantile:int = 10
self.leverage:int = 5

self.market:Symbol = self.AddEquity('SPY', Resolution.Daily).Symbol
# Market daily data.
daily_period:int = 21
self.data[self.market] = SymbolData(daily_period)

self.market_return_data:List[float] = []
self.min_monthly_perf_period:int = 12
self.contrarian_flag:bool = False
self.contrarian_months:int = 0
self.fundamental_count:int = 500
self.fundamental_sorting_key = lambda x: x.DollarVolume
self.selection_flag:int = False
self.UniverseSettings.Resolution = Resolution.Daily
self.Settings.MinimumOrderMarginPortfolioPercentage = 0.
self.AddUniverse(self.FundamentalSelectionFunction)
self.Schedule.On(self.DateRules.MonthEnd(self.market), self.TimeRules.BeforeMarketClose(self.market), self.Selection)        
self.settings.daily_precise_end_time = False
def OnSecuritiesChanged(self, changes: SecurityChanges) -> None:
for security in changes.AddedSecurities:
    security.SetFeeModel(CustomFeeModel())
    security.SetLeverage(self.leverage)
        
def FundamentalSelectionFunction(self, fundamental: List[Fundamental]) -> List[Symbol]:
if not self.selection_flag or self.contrarian_flag:
    return Universe.Unchanged
# Update the rolling window every month.
for stock in fundamental:
    symbol:Symbol = stock.Symbol
    
    # Store monthly price.
    if symbol in self.data:
        self.data[symbol].update(stock.AdjustedPrice)
    
    # Market return calc.
    if self.data[self.market].is_ready():
        self.market_return_data.append(self.data[self.market].performance())

selected:List[Fundamental] = [x for x in fundamental if x.HasFundamentalData and x.Market == 'usa' and x.MarketCap != 0]
if len(selected) > self.fundamental_count:
    selected = [x for x in sorted(selected, key=self.fundamental_sorting_key, reverse=True)[:self.fundamental_count]]
    
# Warmup price rolling windows.
for stock in selected:
    symbol:Symbol = stock.Symbol
    if symbol not in self.data:
        self.data[symbol] = SymbolData(self.period)
        history:DataFrame = self.History(symbol, self.period * 30, Resolution.Daily)
        if history.empty:
            self.Log(f"Not enough data for {symbol} yet.")
            continue
        closes:pd.Series = history.loc[symbol].close
        
        closes_len:int = len(closes.keys())
        # Find monthly closes.
        for index, time_close in enumerate(closes.items()):
            # index out of bounds check.
            if index + 1 < closes_len:
                date_month:int = time_close[0].date().month
                next_date_month:int = closes.keys()[index + 1].month
            
                # Found last day of month.
                if date_month != next_date_month:
                    self.data[symbol].update(time_close[1])
    
performance:Dict[Fundamental, float] = {x : self.data[x.Symbol].performance(1) for x in selected if x.Symbol in self.data and self.data[x.Symbol].is_ready()}

# At least one year of monthly market return is ready.
if len(self.market_return_data) >= self.min_monthly_perf_period and len(performance) >= self.quantile:
    mean_ret:float = np.mean(self.market_return_data)
    std_ret:float = np.std(self.market_return_data)
    recent_market_ret:float = self.market_return_data[-1]

    # There was a crash last month.
    if recent_market_ret < mean_ret - 2*std_ret:
        self.contrarian_flag = True
    
    sorted_by_performance:List[Fundamental] = sorted(performance, key = performance.get, reverse = True)
    quantile:int = int(len(sorted_by_performance) / self.quantile)
    
    long:List[Fundamental] = []
    short:List[Fundamental] = []
    if self.contrarian_flag:
        short = sorted_by_performance[:quantile]
        long = sorted_by_performance[-quantile:]
    else:
        long = sorted_by_performance[:quantile]
        short = sorted_by_performance[-quantile:]

    # Market cap weighting.
    for i, portfolio in enumerate([long, short]):
        mc_sum:float = sum(map(lambda x: x.MarketCap, portfolio))
        for stock in portfolio:
            self.weight[stock.Symbol] = ((-1) ** i) * stock.MarketCap / mc_sum
    
return list(self.weight.keys())
def OnData(self, data: Slice) -> None:
if not self.selection_flag:
    return
self.selection_flag = False

portfolio:List[PortfolioTarget] = [PortfolioTarget(symbol, w) for symbol, w in self.weight.items() if symbol in data and data[symbol]]
self.SetHoldings(portfolio, True)
# Trade execution.
if self.contrarian_flag:
    self.contrarian_months += 1
    if self.contrarian_months == 3:
        self.contrarian_flag = False
        self.contrarian_months = 0
        self.weight.clear()
else:
    self.weight.clear()
def Selection(self) -> None:
self.selection_flag = True

class SymbolData():
def __init__(self, period: int) -> None:
self._price:RollingWindow = RollingWindow[float](period)

def update(self, price: float) -> None:
self._price.Add(price)

def is_ready(self) -> bool:
return self._price.IsReady

# Performance, one month skipped.
def performance(self, values_to_skip = 0) -> float:
return self._price[values_to_skip] / self._price[self._price.Count - 1] - 1

# Custom fee model.
class CustomFeeModel(FeeModel):
def GetOrderFee(self, parameters):
fee = parameters.Security.Price * parameters.Order.AbsoluteQuantity * 0.00005
return OrderFee(CashAmount(fee, "USD"))