Copy Trading Slippage on Polymarket: Why a Late Copy Pays More
A copier never gets the leader’s price. Two separate things push the copy’s price up.
Delay cost
Between the trader’s fill and your order, other people trade. If the trader was right, the price usually moves in their direction — which is against you. That difference between the leader’s price and the market price when you act is the delay cost. It grows with the delay, and it is largest for traders whose edge is speed.
Slippage
Even at a fixed moment there isn’t unlimited size at one price. To fill $100 or $1,000 you may consume several fills at progressively worse prices. That extra cost over the first available price is slippage. It grows with your order size and is worst in thin markets.
- Filled by your order
- Not needed
How we measure both
FollowCheck doesn’t assume a slippage percentage. For each copied buy it walks through the real taker buys that happened after the delay and averages the prices you would have paid (methodology). On every wallet page, the Where the returns go panel shows both costs in dollars, and the Details view on any trade shows the exact fills used.
What changes the simulated cost
- Delay: compare the 0, 1, 5 and 30-minute results on the wallet page.
- Size: try a larger size on the wallet page; slippage usually rises faster than linearly in thin markets.
- Holding period: in our simulations, traders who hold for days lose less to delay than traders who trade on news within minutes.