Quant Buffet放轻松,别过度思虑

股票中的特质因子动量效应

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学术论文

Eureka! A Momentum Strategy that Also Works in Japan

作者作者:Chaves; 机构:The Capital Group Companies

论文摘要

本文探讨了一种动量的替代定义,该定义通过市场回归的特质回报计算得出。通过剔除因市场贝塔敞口导致的回报部分,这种新的动量定义降低了动量策略的波动性,并产生了显著的四因子阿尔法。这些结果不仅适用于美国数据,还在21个国家的样本中得到了验证。最有趣的是,该研究发现这一结论同样适用于日本市场,而此前的研究未能在日本市场中发现传统动量策略的显著有效性。

策略概要

该策略聚焦于在纽约证券交易所(NYSE)、美国证券交易所(AMEX)和纳斯达克(NASDAQ)上市且市值高于NYSE股票第20百分位的大盘股。通过三年的数据,使用CAPM回归估算每只股票的特质回报(残差)。特质动量通过累计残差回报(11个月期间,t-12至t-2月)计算得出。根据特质动量对股票进行五分位排序。策略对最高五分位(动量最强)的股票做多,对最低五分位(动量最弱)的股票做空。投资组合采用等权重配置,并每月进行再平衡,从而利用动量异常实现潜在的超额回报。

策略合理性

学术研究表明,动量策略在市场下跌后和反弹期间往往表现较差。这是因为动量策略中被做空的“输家”组合在市场下跌期间受益,但在市场反弹时遭受显著损失。这些损失与“输家”组合的期权性特征有关。通过专注于特质表现强劲的股票,该策略避开了那些主要因高市场贝塔驱动而表现优异的公司,从而减轻市场反弹的负面影响,并增强基于动量的投资的稳健性。

回测表现

年化收益12.35%
波动率13.25%
贝塔-0.12
夏普比率0.63
索提诺比率-0.033
胜率53%

完整 Python 代码

from scipy import stats
from AlgorithmImports import *
from typing import List, Deque, Tuple
from collections import deque
class IdiosyncraticMomentumStocks(QCAlgorithm):
def Initialize(self) -> None:
self.SetStartDate(2000, 1, 1)
self.SetCash(100000) 
# Daily price data.
self.data:Dict[Symbol, RollingWindow] = {}
self.period:int = 21
self.quantile:int = 5
self.leverage:int = 5
self.exchange_codes:List[str] = ['NYS', 'NAS', 'ASE']
self.symbol:Symbol = self.AddEquity('SPY', Resolution.Daily).Symbol
self.data[self.symbol] = RollingWindow[float](self.period)
self.regression_period:int = 36
self.regression_data:Dict[Symbol, Tuple] = {}

# Monthly residuals for stocks.
self.residuals_period:int = 12
self.residual:Dict[Symbol, RollingWindow] = {}

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

self.fundamental_count:int = 1000
self.fundamental_sorting_key = lambda x: x.DollarVolume
self.selection_flag:bool = False
self.UniverseSettings.Resolution = Resolution.Daily
self.AddUniverse(self.FundamentalSelectionFunction)
self.settings.daily_precise_end_time = False
self.settings.minimum_order_margin_portfolio_percentage = 0.
self.Schedule.On(self.DateRules.MonthEnd(self.symbol), self.TimeRules.AfterMarketOpen(self.symbol), self.Selection)            
def OnSecuritiesChanged(self, changes: SecurityChanges) -> None:
for security in changes.RemovedSecurities:
    symbol:Symbol = security.Symbol
    
    if symbol in self.regression_data:
        del self.regression_data[symbol]
        
    if symbol in self.residual:
        del self.residual[symbol]
        
for security in changes.AddedSecurities:
    symbol:Symbol = security.Symbol
    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 daily price.
    if symbol in self.data:
        self.data[symbol].Add(stock.AdjustedPrice)
if not self.selection_flag:
    return Universe.Unchanged
# selected = [x.Symbol for x in fundamental if x.HasFundamentalData and x.Market == 'usa']
selected:List[Fundamental] = [x for x in fundamental if x.HasFundamentalData and x.Market == 'usa' and x.SecurityReference.ExchangeId in self.exchange_codes]
if len(selected) > self.fundamental_count:
    selected = [x for x in sorted(selected, key=self.fundamental_sorting_key, reverse=True)[:self.fundamental_count]]
idiosyncratic_momentum:Dict[Symbol, float] = {}

# Warmup price rolling windows.
for stock in selected:
    symbol:Symbol = stock.Symbol
    if symbol not in self.data:
        self.data[symbol] = RollingWindow[float](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].Add(close)

    # Market data is not ready.
    if not self.data[self.symbol].IsReady: 
        continue
    market_excess_return:float = self.data[self.symbol][0] / self.data[self.symbol][self.period-1] - 1

    if not self.data[symbol].IsReady:
        continue
    stock_excess_return:float = self.data[symbol][0] / self.data[symbol][self.period-1] - 1
    
    # store regression data
    if symbol not in self.regression_data:
        self.regression_data[symbol] = deque(maxlen = self.regression_period)
    self.regression_data[symbol].append((market_excess_return, stock_excess_return))
    # Regression.
    if len(self.regression_data[symbol]) == self.regression_data[symbol].maxlen:
        # Y = α + (β ∗ X)
        # intercept = alpha
        # slope = beta
        market_excess_returns:List[float] = [x[0] for x in self.regression_data[symbol]]
        stock_excess_returns:List[float] = [x[1] for x in self.regression_data[symbol]]
        
        slope, intercept, r_value, p_value, std_err = stats.linregress(market_excess_returns, stock_excess_returns)
        
        # Calculate every residual for recent months.
        # residuals = []
        # for idx, x in enumerate(market_excess_returns):
        #     yfit = intercept + (slope * x)
        #     residuals.append(yfit - stock_excess_returns[idx])
        # idiosyncratic_momentum[symbol] = sum(residuals[:-2])
        
        # Calculate only latest residual.
        actual_value:float = stock_excess_returns[-1]
        estimate_value:float = intercept + (slope * market_excess_returns[-1])
        residual:float = actual_value - estimate_value
        
        # store residual data
        if symbol not in self.residual:
            self.residual[symbol] = RollingWindow[float](self.residuals_period)
        
        if self.residual[symbol].IsReady:
            # idiosyncratic_momentum[symbol] = self.residual[symbol][1] / self.residual[symbol][self.residuals_period-1] - 1
            idiosyncratic_momentum[symbol] = sum([x for x in self.residual[symbol]][1:])
        
        self.residual[symbol].Add(residual)

if len(idiosyncratic_momentum) >= self.quantile:
    sorted_by_idiosyncratic_momentum:List[Tuple[Symbol, float]] = sorted(idiosyncratic_momentum.items(), key = lambda x: x[1], reverse = True)
    quintile:int = int(len(sorted_by_idiosyncratic_momentum) / 5)
    self.long:List[Symbol] = [x[0] for x in sorted_by_idiosyncratic_momentum[:quintile]]
    self.short:List[Symbol] = [x[0] for x in sorted_by_idiosyncratic_momentum[-quintile:]]

return self.long + self.short

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()
def Selection(self) -> None:
self.selection_flag = True
# Custom fee model
class CustomFeeModel(FeeModel):
def GetOrderFee(self, parameters):
fee = parameters.Security.Price * parameters.Order.AbsoluteQuantity * 0.00005
return OrderFee(CashAmount(fee, "USD"))