Backtest Basics

A “backtest” is a model, or simulation, of how a symphony may have performed in the past based-on historical data. There are some important assumptions to understand and consider when using backtests in Composer. Below, we outline these assumptions and key differences between backtesting and live trading symphonies. 

Key facts

  • All backtest statistics are hypothetical and have been designed with the benefit of hindsight.
  • Backtests do not take into account the actual costs that may result from live trading of the symphony.
  • Past performance is not a reliable indicator of future performance.
  • All backtests are estimations of how the model will perform over time, in certain market environments, and are not an indicator or recommendation of any individual trading decisions either in the past or the future.

Data sources

To simulate past decisions and calculate return statistics, backtests use daily adjusted closing prices of assets making up the symphony over the backtest period. Adjusted closing prices reflect a security’s closing price adjusted for any corporate actions, such as stock splits or dividends. As such, these prices don’t represent real quotes from any point during the trading day.

When a symphony is traded live, trading decisions are made during the trading period using realtime data, which represent real quotes on the market. For this reason, as well as others below, actions chosen in a backtest and the assets selected should not be directly compared against those made by live trading symphonies.

Time of day

The symphony trading period runs from 3 to 4pm eastern on days the market is open. If there is significant market volatility near the end of the day–after the start of the trading period–symphony decisions made during the trading period may be different than those that would be made if using the day’s closing prices. 

If volatility is high during the trading period, decisions made by different instances of the same symphony may also vary due to differences in quotes received at the precise time that each symphony is executed. 

Dividend reinvestment

Backtests assume that all dividends and distributions received from symphony assets are reinvested.

For live trading symphonies, dividends and distributions received from symphony assets are currently not automatically reinvested. Instead, these distributions are added to the cash balance of a user’s account, and can be reinvested manually by adding a new investment to the symphony.

Slippage and fees

Backtests account for simulated slippage and fees. 

The model simulates slippage of 0.05% per transaction over the course of the backtest. When trading a symphony, actual slippage can be higher or lower than this assumption. For low-volume tickers, slippage can sometimes be higher, while high-volume tickers generally have more liquidity and won’t execute with much, if any, slippage. 

The model also accounts for hypothetical regulatory fees on sales from the US Securities & Exchange Commission (SEC) and Financial Industry Regulatory Authority (FINRA). These are the same types of fees that are charged on sales of assets in live-trading symphonies. Composer does not benefit from these fees, and all proceeds go directly to the SEC and FINRA. 

From our brokerage partner, Alpaca, the fees applied to the backtest and in live trading are as follows:

  • SEC: $5.10 per $1,000,000 of principal (sells only) - this fee is rounded up to the nearest penny on each fill or partial-fill.
  • FINRA Trading Activity Fee (TAF): $.000119 per share (sells only) - this fee is rounded up to the nearest penny on each fill or partial fill and will be no greater than $5.95.

Backtests on other trading platforms

Backtests on other platforms may make different assumptions than those used to create backtests in Composer. We encourage users to understand the full details and assumptions of backtests before making any comparisons.

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