Obviously rankings are subjective. This is intended to give the collector a feel for how many of a particular item are out there (if known) which in turn, can play into value. Value should not be confused with rarity however. Just because a crayon box is highly desirable within the hobby doesn't change how it would rate in terms of rarity. And just because an item is unique or very rare, it does not guarantee desirability. It is generally the market that determines value based on desirability (and let's not forget condition). This can be misleading when collecting because in many cases, there may be just a few collectors willing to pay premiums on an item but once these collectors have been taken care of, the value of the item goes way down. Rarity rankings will help to alleviate some of the "it may never show up again" syndrome that many collectors fall into. It will not address the "I must have it regardless of its value" attitudes of the fanatic collectors.
Having said all of this, it will also be difficult to keep these rankings real accurate. Items that were unique may turn up again. I will try to keep the rankings accurate but will need help from you. If you see something that doesn't look right - let me know and I'll get it resolved. The more accurate the information, the more useful this site will become.
1 - Available now. Can be readily obtained in stores if desired.
2 - Easy. Easily obtainable, large quanitities out there.
3 - Common. Rarely does a month go by without one showing up.
4 - Average. This shows up with regularity several times per year.
5 - Scarce. These may only show up only two or three times per year.
6 - Tough. They are out there, but only show up infrequently. May have had a small find.
7 - Rare. More than 5 but less than, say, 20. No finds greater than 2 or 3.
8 - Very Rare. Approximately 1 to 5 known.
9 - Unique. Only one known.
10 - Unknown. No versions known - only documentation exists.