Just some thoughts on CB Gravity, Popularity and how to pick CB products. I evaluated only vendors that have a Spotlight page so that I could get the number of subscribers. I found the following:
1) The correlation (see Pearson's correlation coefficient) between Gravity and the number of Subscribers is 0.64290, which is a fairly strong correlation. When discussing Gravity CB (and many 3rd party articles about it, including this forum) always talk about sales, timing, etc. But ... a correlation of 0.64 between Gravity and the number of subscribers indicates that Gravity is, on average, going to be high whenever the number of subscribers is high (and the reverse, of course).
2) The correlation between Gravity and Popularity is 0.81705. This is a very strong correlation. According to CB, both Gravity and Popularity use some really complicated formulas that take into consideration the number of sales, affiliates, time and whatever. But ... however complicated their formula are, the one thing that they cannot do is hide their tracks! A correlation of 0.8+ means that Popularity and Subscribers move almost in lockstep. As we saw above, Popularity and Gravity also move together, although the correlation is lower because sales count for more in the Gravity computation.
3) Gravity and Avg. Sale are almost uncorrelated (-0.15). All this means is that expensive products tend to have somewhat lower Gravity than cheaper ones, but the correlation is weak.
4) The correlation between the Number of Subscribers and Popularity is 0.52, which is moderately strong.
5) The correlation between the number of subscribers and the average sale is almost zero (-0.05). This is a bit surprising, in that it tells us that both cheap and expensive products are able to gather affiliates.
6) The correlation between Popularity and the average sale price is low and negative (-0.20). Again, all this tells us is that affiliates in general have some aversion to promoting very expensive products, probably because they think that these products will be difficult to sell, but the correlation is weak.
How to use this information
Basically, we are looking at discrepancies between the actual and expected figures.
For this analysis I looked at the Cooking, Food & Wine section in CB (not my niche, I am an omnivorous geek partial to real Spanish food). Let's compare a few products. The first three are in the Paleo diet BS fad category (no, we did not evolve to eat this type of food; we evolved long legs and distance-running traits to run our prey down and be the first to scavenge a carcass. Try that ...):
Product #1: Paleo Recipe Book - Brand New Paleo Cookbook
Subscribers: ??? (No Vendor Spotlight, so we need to estimate, see below)
Popularity Ranking In Category: 1
Gravity has been steady for the last 3 months around 130 or so.
% Referred hovers around 20% (Bad! This means this vendor is generating 75% of their sales from non-affiliate sales).
Given the correlation between Popularity (Rank=1), Gravity (128) and # of Subscribers our estimate for this
product needs to be 250+ affiliates.
Product #2: Paleo Cookbooks - Complete Paleo Recipe Guide To Healthy Eating
Popularity Ranking In Category: 2
Gravity has been steady for the last 3 months around 40 or so.
% Referred at 75% and growing (Good! This means the vendor generates 75% of their sales through affiliates).
Product #3: Caveman Feast: 210+ Paleo Recipes From Civilized Caveman Cooking
Subscribers: ??? (No Vendor Spotlight, so we need to estimate, see below)
Popularity Ranking In Category: 4
Gravity has been hopping around between 20 and 30 for the last 3 months, and it is decreasing.
% Referred hovers around 25% (Bad! This means this vendor is generating 75% of their sales from non-affiliate sales).
Given the correlation between Popularity (Rank=4), Gravity (22.6) and # of Subscribers our estimate for this
product needs to be 50+ affiliates.
If you are going to jump into the Paleo Diet fad the vendor #2 is likely going to generate more and better sales for you.
The first vendor is hyped-up to the max, has a ton of affiliates (and therefore a lot of competition) but *most* of their sales
are not coming from affiliates (why?). The third vendor has the same problem in that 75% of their sales are not coming through affiliates, and in fact looks like it has been losing affiliates.
Vendor #2 looks much better, in that their popularity ranking coincides with their gravity, they have about the right number of affiliates and the majority of their sales is actually coming from affiliates.
Product #4: Guilt Free Desserts: Gluten Free Diabetic Safe Desserts
Popularity Ranking In Category: 3
Gravity has been steady for the last 3 months between 20 and 25.
% Referred at 70% but coming down a bit lately (Good! This means the vendor generates about 70% of their sales through affiliates, but the decreasing trend might mean the vendor is also beginnig to use other channels).
Product #5: As Seen On Tv. Make Your Favorite Restaurant Dishes At Home!
Popularity Ranking In Category: 5
Gravity has been steady for the last 3 months between 25 and 30.
% Referred at about 80%, which is good, but there was a big drop to about 55% in Frebruary and then it went back up. This is worrisome because it means that this vendor had a big increase in sales from non-affiliate channels. This was probably their own promotion, but it means you are competing against your own vendor.
I would pick vendor #4. Steady gravity, steady % Referrals, the relationship between the number of affiliates (63) and their Gravity (24.75) looks like the Gravity is coming from a lot of sales from a lot of affiliates, rather than just one or two super-affiliates. What I mean by this is that Vendor #4 seems to have a positive discrepancy between the number of affiliates and their Gravity, and this works in your favor.
Vendor #5 also has a discrepancy between the Gravity and the # of affiliates, and a big one, but not in your favor. Given the correlation that we found between the number of affiliates and the Gravity we would not expect to see 326 affiliates for this product! Between this and the drop in % Referred (xtra-hype-promo anyone) I would stay away from this one.
Product #6: Gluten Free Low Glycemic Cookbook For Diabetics & Allergy Sufferers
Popularity Ranking In Category: 9
Gravity has jumping around a bit for the last 3 months between 4 and 9.
% Referred is almost 100%. This is excellent, as this vendor makes money exclusively through affilate sales.
Product #7: The Home Winemaker's Inner Circle
Popularity Ranking In Category: 33
Gravity has jumping around for the last 3 months between 1.7 and 4, with a decreasing trend.
% Referred is barely 25% with a very large drop from 75% three months ago (Bad!)
I would pick vendor #6 over vendor #7. Both are relatively low-volume sellers, but product #6 has a discrepancy between the number of subscribers (63) and their Gravity that indicates multiple sales by many affiliates. Looks like a slow-but-steady seller.
Product #7 got problems. First, there is a big discrepancy between the number of affiliates (55) and the Gravity (1.87, which is very low). Given the correlation that we saw above this product has many more affiliates than we should expect (and the discrepancy is not in our favor). The jump down from 75% in the number of % Referred indicates a big promotion by the vendor (perhaps because their affiliate sales were very slow). The 25% Referred is very, very low.