This short blog is in response to a recent support ticket querying whether particular domains display significant differences in terms of the ratio of referring subnets to referring IP addresses. We were asked what a “normal” value of this ratio could be.
A statistical study was performed on the Majestic Million data. We found that typical values lay within the range 1.2 to 1.8, and in general were less than 2. Figure 1 shows a scatter plot of the number of referring IPs versus that of referring subnets. Note that the “Big 4”, namely, Google, Facebook, YouTube and Twitter (having global ranks of 1, 2, 3 and 4 respectively) are highlighted.
Figure 1: Scatterplot of Referring IPs versus Referring Subnets
Figure 2 plots the ratio of the referring subnets to the referring IP addresses for the Majestic Million data plotted as a function of the global rank. The data are dispersed about a mean value of 1.233 with a standard deviation (shown by the red dashed lines) of 0.173, and a high correlation of 0.873.
Figure 2: Ratio of Referring IPs to Referring Subnets as a function of Global Rank
The histogram of the ratios shown in figure 3 displays a very high skewness to the left, with the highest number of values occurring between 1.2 and 1.3. The cumulative distribution shown in figure 4 demonstrates that 99% of the ratio values lie within 1.8.
Figure 3: Histogram of Referring Subnets/ Referring IPs Ratio
Figure 4: Cumulative Distribution of Referring Subnet/ IP Ratio
The table below shows the top 45 domain names in the Majestic Million listed in descending order of the ratio. The first 10 are highlighted in yellow. For comparison purposes, the first four globally ranked domains are also displayed highlighted in green.
Unsurprisingly, the table shows that, outside of the top 4, many domains names in the table appear to be from hosting companies, suggesting that the ratio may vary to some extent within different industries.