Signal Turnover, Breadth and Neutralization

Every time a signal changes, a portfolio must trade to follow it, and every trade costs money. Turnover measures how much of a portfolio is bought and sold over a period. Fast changing signals produce high turnover and high costs; slow signals produce low turnover. The art of portfolio management is to capture as much of a signal's predictive power as possible while keeping turnover, and therefore costs, under control.

Measuring turnover#

A common definition for a portfolio:

turnover = (sum of absolute changes in weights) / 2, per rebalance
annual turnover = turnover per rebalance × number of rebalances per year

An annual turnover of 100% means, roughly, that the whole portfolio is replaced once a year. Some sources count both buys and sells (without dividing by 2), so check definitions.

Turnover by strategy type#

Approximate ranges; actual figures depend on construction.

Turnover, decay and costs#

Techniques to reduce turnover#

Buffers in practice#

A ranking strategy might buy stocks entering the top 10% but sell only when they fall below the top 20%. This hysteresis keeps stocks hovering near the cutoff from being bought and sold repeatedly, cutting turnover sharply with little loss of signal. See Rebalancing.

Optimal trading speed#

Nicolae Gârleanu and Lasse Pedersen (2013) showed mathematically that the optimal approach is to trade partway toward the target portfolio, moving faster for signals that decay quickly and slower for persistent ones, and to aim at a blend of current and expected future targets. This formalises the intuition that patient trading saves costs.

Turnover and capacity#

Higher turnover means more trading per dollar managed, which reduces capacity. A strategy with 1,000% turnover will hit market impact limits at a much smaller size than one with 100% turnover. See Alpha Capacity and Crowding.

Taxes#

In taxable accounts, high turnover realises gains frequently and may convert long term gains into short term ones, which are often taxed more heavily. See Trading Taxes and Capital Gains.

Frequently asked questions#

What is portfolio turnover?#

A measure of how much of a portfolio is traded over a period, often expressed as a percentage of the portfolio's value per year.

Why does turnover matter?#

Because every trade incurs costs, and high turnover can erase a strategy's edge, reduce capacity and increase taxes.

How can I reduce turnover without losing returns?#

Use no trade buffers, smooth signals, choose a sensible rebalancing frequency, net trades across signals and include costs in portfolio construction.

Next, learn the systematic sources of return in Factor Investing Explained.