Copy trading and the lag between master and follower

[Shadow Trader]

Social trading and trade copiers replicate one account's trades onto others. In theory, the follower gets the same entries and exits. In practice, there's a delay.

The delay has several parts: the master's order is detected, transmitted, and re-executed on the follower's account. Each step takes time, and the follower's broker may have different prices and spreads.

For slow strategies, a second of lag doesn't matter. For scalping, it's a deal-breaker. A master entry at 1.1000 might be copied at 1.1002, and the exit at 1.1004 copied at 1.1003. A 4 pip master gain becomes a 1 pip follower gain.

The lag gets worse with many followers, since the system has to process lots of copies at once, and the later ones fill at worse prices.

For a master, the effect shows up as complaints from followers whose results are far below the displayed performance. For a follower, it shows as a gap between the signal provider's reported results and what the account earns.

Short-term strategies are generally a poor fit for copying, and the numbers on the leaderboard rarely reflect the follower experience.

What gap between master and follower results has been seen, and was it explained by lag?