The closing line is the last price a market offers before it stops taking action. It is the most informed number the market ever produces, because every piece of information and every dollar of opinion has been folded into it by then.
Closing line value asks a narrow question: was the price you took better than the closing price? If it consistently was, your process is finding something before the market does. If it consistently was not, your wins are luck running ahead of a losing method.
How to measure it properly
- De-vig the price you took, using the opposing side at the same moment.
- De-vig the closing price, using the opposing side at the close.
- Compare the two fair probabilities. The difference, in percentage points, is your CLV.
Skipping the de-vig step is the most common error. Comparing a raw entry price to a raw closing price measures the difference in book margin as much as the difference in market opinion, especially if the two prices came from different books.
What CLV does not tell you
- It does not predict your next result. Positive CLV and a losing month happen together constantly.
- It does not survive being measured after the event started. Once a game is in progress, the gap between your entry and the close is mostly game state.
- It does not prove profitability by itself, because you still have to beat the vig you actually paid.
Note
This is exactly why the VigPulse public ledger reports CLV only on pre-game entries, and marks in-play rows as n/a. The in-play numbers in that experiment reach several hundred percent, which measures innings elapsed, not price discovery.