On Robustness of Double Linear Trading With Transaction Costs

A trading system is said to be robust if it generates a positive return regardless of market direction. To this end, a consistently positive expected trading gain is often used as a robustness metric for a trading system. In this letter, we propose a new class of trading policies called the double linear policy in an asset trading scenario when transaction costs are involved. Unlike many existing papers, we first show that the desired robust positive expected gain may disappear when transaction costs are involved. Then we quantify under what conditions the desired positivity can still be preserved. In addition, we conduct heavy Monte-Carlo simulations for an underlying asset whose prices are governed by a geometric Brownian motion with jumps to validate our theory. A more realistic backtesting example involving historical data for cryptocurrency Bitcoin-USD is also studied.