4688 MLB trades, 1985–2026, each graded on what every player was expected to produce at the time — a Bayesian estimate blending his pedigree with his recent track record, over the years of team control acquired — versus what he actually produced for his new team. The ± figure on Exp is a historically calibrated predictive standard deviation, measuring how widely comparable forecasts have missed around their expected value. That spread is the reason individual trade outcomes remain so difficult to foresee. Shown by default as surplus value (that production priced at the FA market rate of a win, minus salary — so cheap, cost-controlled players carry the most value); toggle to raw WAR up top. Filter, sort — and click any trade for its own shareable page showing how each player's expected value was built (pedigree prior, recent form, control horizon). Descriptive, not a skill claim — who won a trade is ~99% unforeseeable at the time. A #N badge on a player = his Baseball America top-100 prospect rank that year (hover for detail).