Carson Cistulli is working through an excellent series looking at the demographics of a "good" player, which he defined as any player who posted at least 3 WAR in any one season from 2010-2014. Yesterday's edition focused on players who had been drafted, which, based on his prior article, account for about 75% of all good players during that stretch (the others being international or undrafted free agents). He broke them down by draft round. Here's what he found for high school draftees:
College players broke down in much the same manner. There was an interesting difference for junior college draftees, but nevertheless the result is really clear: about half of all players who put up a well above-average season are taken in the first round. Half!
A lot of fans and people in the media tend to discount importance of draft status in baseball, sometimes equating it to a crapshoot. We see first-round busts all the time, and we see players who were drafted much later in the draft who put up big numbers. Nevertheless, every time there's a study done, we see that first round players are far better bets to be productive, and (from other studies) produce far more wins for their teams than later-round selections.
Another small point: the draft is almost entirely the domain of the scout. Developing baseball players is prone to enormous uncertainty. Nevertheless, scouts still do a really good job of identifying the best players to take in the early rounds of the draft.