I don't think you have this Law of Total Tricks (LoTT or "The Law") quite right for several reasons. As one of my wise teachers once counseled me, "When something seems too good to be true, it probably is." I assert that The Law is no exception to this maxim. Here is why: 1. The Law is not a law of nature as the noun "law" might suggest. Rather, it is an empirically observed statistical or probablistic tendency whereby the total tricks available to both partnerships (playing in their best respective trump fits and both sides playing double dummy) is equal to the summed total number of trumps in those best fits. That is, the correspondence between total tricks and total trumps is typical, but not guaranteed. When the total number of trumps is 18 or fewer, it is fairly unusual for The Law to disappoint but it can. When the total number of trump increases above 18, it is not uncommon for the total tricks to be off by 1 or 2 (and occasionally even more) tricks than the number predicted by the number of total trumps. Proponents and critics of The Law have identified characteristics of situations when The Law's predictive powers are diminished, but as far as I know nobody has been able to produce a set of reliable "correction factor" rules allowing players to make consistently accurate adjustments. 2. Even if The Law were a true law - i.e., an error-free or perfect predictor of total tricks based on total trumps - it would still be relegated to a tool that includes risk in use. One never knows the total number of trumps for sure. Rather, one must one estimate or infer the LIKELY total number of trumps based on the auction. Some bids imply a certain length in a suit, but a greater number (and sometimes a fewer number) may be held by a player showing length. Lively competitive auctions tend to increase the likelihood of extra length being held by one or more players, for example. 3. Vulnerability DOES matter. For example, at Match Points or Board-A-Match, even a 1 trick set when doubled and vulnerable (-200) is often a very poor result in a part score deal. Likewise, sacrifices at IMPs can be overly costly when vulnerable and especially so when the opponents are not. In summary, the thing to remember that The Law is a first approximation guideline to be considered, not slavishly followed much in the same way that honor values are the first order approximation of a hand's offensive and defensive trick taking potential in the early rounds of the auction while being subject to (sometimes dramatic) changes based on what is learned about the degree of fit or support for both partner's suit lengths and high card values as the auction develops and unfolds. It is a simple tool and can be quite helpful when judiciously applied and considered. But simple decision support tools don't always produce accurate results when applied to complex circumstances. Megan BBO user "Case_No_6"