從Optimal Trading Strategies開始：
There are two main reasons why traders execute orders using a VWAP trading strategy. First, a VWAP strategy is the trading strategy that minimizes market impact cost. Traders executing orders utilizing VWAP strategies are interested in participating with market volumes so to cause the least disruption to the supply-demand imbalance in each period. Second, for many traders their execution performance is measured against the VWAP benchmark. An average execution price more favorable than the VWAP price benchmark is considered high-quality performance while an average execution price less favorable than the VWAP benchmark is considered inadequate performance.
但是，當涉及回測時，市場影響因此假定為零。一個人假設他不會影響市場，因為大眾基準價格保持不變。那麼，一個人如何能更有效，更現實地回溯他的VWAP策略呢？