  We analyze a proprietary dataset of trades by a single asset manager,
comparing their price impact with that of the trades of the rest of the market.
In the context of a linear propagator model we find no significant difference
between the two, suggesting that both the magnitude and time dependence of
impact are universal in anonymous, electronic markets. This result is important
as optimal execution policies often rely on propagators calibrated on anonymous
data. We also find evidence that in the wake of a trade the order flow of other
market participants first adds further copy-cat trades enhancing price impact
on very short time scales. The induced order flow then quickly inverts, thereby
contributing to impact decay.
