ETF Sector Rotation: Backtesting Momentum-Based Allocation
# ETF Sector Rotation: Backtesting Momentum-Based Allocation
Sector rotation is the idea that different sectors of the economy lead at different times, and by rotating into the strongest sectors, you can outperform a static allocation. We backtested this concept using momentum signals across the eleven SPDR sector ETFs.
Strategy Design
The rules were straightforward: each month, rank all eleven sector ETFs by their trailing 6-month total return. Go long the top three sectors with equal weight, hold for one month, then rebalance. If any of the top three sectors have negative absolute momentum, replace them with short-term Treasury ETFs (SHY).
Data and Timeframe
We tested from 2000 through 2025 using adjusted close prices that account for dividends. This gives us multiple full market cycles including the dot-com bust, the 2008 financial crisis, COVID crash, and the 2022 bear market. Commissions were set at zero to reflect modern broker pricing.
Headline Results
The sector rotation strategy returned 11.3% annualized versus 9.8% for SPY buy-and-hold over the same period. However, the real advantage was in risk-adjusted terms: the strategy achieved a Sharpe ratio of 0.72 versus 0.54 for SPY, with maximum drawdown of 28% compared to 55% for SPY.
Where It Excelled
The strategy massively outperformed during trending markets. In 2003-2007, it rode energy and materials during the commodity supercycle. In 2020-2021, it concentrated in technology and consumer discretionary during the pandemic rally. Momentum works when trends persist, and sectors tend to trend for months or years.
Where It Struggled
The strategy gave back significant gains during sharp reversals and choppy markets. In 2009, it was slow to rotate from defensive sectors into the recovery leaders, missing the first 20% of the rally. Similarly, in late 2022 into 2023, rapid rotations between value and growth sectors caused whipsaw losses.
The Absolute Momentum Filter Saved the Strategy
Without the Treasury filter for negative momentum, the strategy suffered a 41% maximum drawdown in 2008 instead of 28%. The simple rule of requiring positive absolute returns prevented the strategy from holding sectors in freefall, even if they were the "best" of a bad bunch.
Lookback Period Sensitivity
We tested 3-month, 6-month, 9-month, and 12-month lookback periods. The 6-month lookback produced the best Sharpe ratio, while the 12-month lookback produced slightly higher total returns with larger drawdowns. The 3-month lookback generated excessive turnover and underperformed all alternatives.
Tax and Implementation Considerations
Monthly rebalancing generates significant short-term capital gains. On an after-tax basis, the strategy advantage over buy-and-hold narrows considerably for taxable accounts. In tax-advantaged accounts like IRAs, sector rotation retains its full advantage.
Final Verdict
Momentum-based sector rotation has genuine historical edge, but it requires patience through choppy periods and discipline during drawdowns. The absolute momentum filter is not optional but essential. Traders implementing this strategy should expect 2-3 years of underperformance within any decade-long period, making it unsuitable as a sole strategy for most investors.