Quant BuffetRelax, Not Over Thinking

Industry Herding and Momentum

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Academic paper

Strategy in a nutshell

Targets 49 Fama-French industries, identifying low-herding industries via normalized CSSD. Goes long on the top 50% and short on the bottom 50% of industries by six-month momentum, with equally weighted portfolios rebalanced monthly.

Economic rationale

Low-herding industries reduce crowding effects, allowing momentum strategies to be more effective. Sorting by past six-month returns within these industries captures predictable return patterns while mitigating herding-driven distortions.

Backtest performance

Annualised return14.43%
Volatility30.7%
Beta-0.076
Sharpe ratio0.34
Sortino ratio-0.284
Win rate50%

Full Python code

from AlgorithmImports import *
import numpy as np
from typing import List, Dict, Tuple
class IndustryHerdingandMomentum(QCAlgorithm):

def Initialize(self):
self.SetStartDate(2003, 1, 1)
self.SetCash(100000)
self.period:int = 7 * 21
self.leverage:int = 5
self.min_share_price:int = 5
self.min_stocks:int = 5
# Daily price data.
self.data:Dict[Symbol, SymbolData] = {}

market:Symbol = self.AddEquity('SPY', Resolution.Daily).Symbol

self.long:List[Symbol] = []
self.short:List[Symbol] = []

# Historical industry CSSD data.
self.industry_CSSD:Dict[str, float] = {}
self.cssd_period:int = 3    # Minimum cssd data period.

self.fundamental_count:int = 1000
self.fundamental_sorting_key = lambda x: x.DollarVolume
self.selection_flag:bool = True
self.Settings.MinimumOrderMarginPortfolioPercentage = 0.
self.UniverseSettings.Resolution = Resolution.Daily
self.AddUniverse(self.FundamentalSelectionFunction)
self.Schedule.On(self.DateRules.MonthEnd(market), self.TimeRules.AfterMarketOpen(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]:
# Update the rolling window every day.
for stock in fundamental:
    symbol:Symbol = stock.Symbol
    # Store monthly price.
    if symbol in self.data:
        self.data[symbol].update(stock.AdjustedPrice)
if not self.selection_flag:
    return Universe.Unchanged
selected:List[Fundamental] = [
    x for x in fundamental if x.HasFundamentalData and x.Market == 'usa' and x.Price >= self.min_share_price 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]]
industry_group:Dict[str, List[Symbol]] = {}
# 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, Resolution.Daily)
        if history.empty:
            self.Log(f"Not enough data for {symbol} yet")
            continue
        closes:Series = history.loc[symbol].close
        for time, close in closes.items():
            self.data[symbol].update(close)
    if not self.data[symbol].is_ready():
        continue

    # Adding stocks in groups
    industry_group_code:str = stock.AssetClassification.MorningstarIndustryGroupCode
    
    if industry_group_code == 0: continue
    
    if not industry_group_code in industry_group:
        industry_group[industry_group_code] = []
    industry_group[industry_group_code].append(symbol)

# CSSD calc.
cssd_performance_data:Dict[str, Tuple[float]] = {}
for group_code, group_symbols in industry_group.items():
    # Groups with at least 5 stocks, so CSSD is worth to calculate.
    if len(group_symbols) >= self.min_stocks:
        # Calculate CSSD.
        performance_1M:List[float] = []      # Last month's performance to calculate CSSD.
        performance_6M:List[float] = []      # 6M momentum.
        
        for symbol in group_symbols:
            performances:Tuple[float] = self.data[symbol].performances()
            performance_1M.append(performances[0]) # Last month performance
            performance_6M.append(performances[1]) # First six months performance
                
        if len(performance_1M) >= self.min_stocks and len(performance_1M) == len(performance_6M):
            avg_return:float = np.mean(performance_1M)
            cssd:float = sqrt( ( sum([(x-avg_return)**2 for x in performance_1M]) / (len(performance_1M)-1) ) )
            
            if group_code not in self.industry_CSSD:
                self.industry_CSSD[group_code] = []
            
            if len(self.industry_CSSD[group_code]) >= self.cssd_period:
                normalized_cssd:float = (cssd - np.mean(self.industry_CSSD[group_code])) / np.std(self.industry_CSSD[group_code])
                avg_momentum:float = np.mean(performance_6M)  # Group average momentum for last 6 months. (skipped last one)
                
                cssd_performance_data[group_code] = (normalized_cssd, avg_momentum)
                
            self.industry_CSSD[group_code].append(cssd)

if len(cssd_performance_data) != 0:
    sorted_by_cssd:List[Tuple[str, float]] = sorted(cssd_performance_data.items(), key = lambda x: x[1][0], reverse = True)
    count:int = int(len(sorted_by_cssd) * 0.3)
    low_herding:List[Tuple[str, float]] = [x for x in sorted_by_cssd[:count]]
    
    sorted_by_momentum:List[Tuple[str, float]] = sorted(low_herding, key = lambda x: x[1][1], reverse = True)
    count:int = int(len(sorted_by_momentum) * 0.5)
    long_groups:List[str] = [x[0] for x in sorted_by_momentum[:count]]
    short_groups:List[str] = [x[0] for x in sorted_by_momentum[-count:]]
    
    self.long:List[Symbol] = [symbol for x in long_groups for symbol in industry_group[x]]
    self.short:List[Symbol] = [symbol for x in short_groups for symbol in industry_group[x]]

return self.long + self.short
                
def Selection(self) -> None:
self.selection_flag = True

def OnData(self, data: Slice) -> None:
if not self.selection_flag:
    return
self.selection_flag = False
# Trade execution.
targets:List[PortfolioTarget] = []
for i, portfolio in enumerate([self.long, self.short]):
    for symbol in portfolio:
        if symbol in data and data[symbol]:
            targets.append(PortfolioTarget(symbol, ((-1) ** i) / len(portfolio)))

self.SetHoldings(targets, True)

self.long.clear()
self.short.clear()

class SymbolData():
def __init__(self, period:int):
self._monthly_closes:RollingWindow = RollingWindow[float](period)

def update(self, close:float) -> None:
self._monthly_closes.Add(close)

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

def performances(self) -> Tuple[float]:
monthly_closes:List[float] = list(self._monthly_closes)
last_month:List[float] = monthly_closes[:21]
first_six_months:List[float] = monthly_closes[21:]

last_month_performance:float = last_month[0] / last_month[-1] - 1
first_months_performance:float = first_six_months[0] / first_six_months[-1] - 1

return (last_month_performance, first_months_performance)

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