SEOmoz yesterday launched MozCast which is a weather forecast but for Google algorithms. When you visit the website you will notice their is a picture and a temperature next to it, the hotter and stormier the weather shown, the more Google’s rankings have changed. Although algorithms such as Penguin and Panda seem to get all the attention, Google have actually revealed that they made around 516 changes last year and evidence seems to suggest that this pace will only continue. This is where MozCast comes in, helping you to keep track of the day-to-day changes that Google make. Below is a screenshot of just what a algorithm report on MozCast looks like:
How Does MozCast Work?
Every 24 hours MozCast will handpick a selection of 1000 keywords, after a little keyword analysis, and then grab the top 10 Google organic search result, the keywords were deliberately chosen to avoid any obvious local intent, these are then dispersed equally across 5 “bins” by query volume. These are then tracked at more or less the same time each day from exactly the same location. By doing this they are ensuring that they keep the data set tightly controlled.
Every day MozCast then take the present top 10 and compare it with the previous day’s top 10 (for any particular keyword), they then calculate the rate of change otherwise known as “delta”. In particular, MozCast use two different metrics one called Delta 100 and one called Delta10, these measure the changes across the whole set of top 10 results. Then they crunch Delta10 across all 1,000 keywords and multiply the resulting average by a set multiplier (which is currently 28.0) to produce something that looks like a temperature (in °F). An average day comes out at about 70°F.
First Of All, What is Delta 10?
Here comes the more complicated version of the story,MozCast tried a lot of metrics to be able to compare the two sets of top 10 results, in the end they landed on two that seemed to work pretty well and were seemingly simple enough to explain. The first one being “Delta100″, for any two days of top 10 rankings, it then provides us with a number from 0-100 which is then calculated using the following rules:
Should a ranking move at all, then “#” is the number of spots that it will move, in other words, if a URL drops from the #3 spot to the #6 spot, then +3 would get added on to Delta100 for that chosen keyword. Across all of the 1,000 keywords, Delta100 looks like a power curve, so in order to regularize the data (and make statistics like the mean and standard deviation easy to calculate), MozCast will take the square root of Delta100 to then go ahead and create Delta10 (this is called delta10 because it theoretically ranges from 0-10). All temperatures and long-term reports on MozCast are directly based off of Delta10.