He explains it here...
"Here is my current list of Top 175 MLB prospects for 2016. This revises and expands the Top 50/50 List published in the 2016 Baseball Prospect Book.. Grades here supersede previously published lists and rankings.
The rankings are based on a combination of sabermetrics; scouting reports (including publicly available reports and private reports from friends or contacts), video, in-person views when possible, and some measure of intuition. My lists weigh closeness to the majors and risk as well as pure upside. A list based on pure upside with less regard for risk would look quite different. I try to find a balance between the two factors.
Every list has quirks, of course, reflecting the filters and biases of the analyst. Ultimately these are my opinions and I take sole responsibility for them. Many of my rankings are in line with industry consensus, but some are not.
Thinking and analysis change constantly, so look at this as a snapshot of how things stand in late March. Such lists can be tinkered with forever but at some point you have to press the "publish" button. I will be around in the comments thread today to answer questions.
Once you get past the Top 100 especially, you should take a "neighborhood" tier approach rather than "this guy at 129 is clearly better than the guy at 130." "