INTRO: RPM in full is Revenue Per Mille (The word, "mille" has French roots, meaning thousand. It is contained in some English words such as millennium, meaning a thousand years). RPM is all about the amount of money that you will earn from each 1000 views (impressions) of the ads on your website. If you see for instance, $5 as your RPM on your Adsense Dashborad, it means that you will earn the equivalent amount with a thousand ad impressions on your website. But then, you noticed that your RPM has reduced to a pitiable level, or that it is constantly reducing and you want to know the reason. There are several reasons for the reduction of your RPM, and below are some of the reasons.
1) Social Media Traffics: This is unbelievable but it is true! Traffics from social media such as Facebook sends RPM of Adsense accounts crashing. The reason is not far-fetched. Social media traffic is less reputable in the blogworld. It could easily be sent in swarms into a website. Google dislikes it because it gives little or no value to the advertizers. It is no longer news that Google puts advertizers' interests first and does everything possible to give value to the money they spend on adverts on Google Ads Network. You can imagine what will happen to advertizers' budget if a sensational news link for instance is shared on a Facebook group of 250,000 members. The website could receive several thousands of visitors within 5 munites. In that situation, Google simply reduces the RPM so that the resulting several thousands of ads impressions will add little or nothing to your earning. It is therefore advisable to write rich and useful contents that will send traffics to your website from search engines; and stop puting links to your website on social media.
2) Location of the Audience: Advertizers bid more for audience from locations of interest. Generally however, visitors from Europe and the United States of America command higher RPM while Asian audience command lower RPM. This geographical differences in RPM rates, oko.uk argues, are due to not just by the spending power of the individuals in those countries, but by how established the online adverting market is in those countries.
3) Ad placement and Size: The size of Adsense banners and there placements is another reason for low RPM. Large-sized ad banners have been found to be performing better than smaller ones. The most popular in better performance however is 300×250. Ads placed in less-interest parts of a website could consistently fail to capture the interest of the website user and this affects the RPM.
4) Topic/Niche: Blogs and websites on high-demand keywords such as finance command higher RPM. Also, advertizers prefer to bid higher on targeted micro-niches than general topic blogs. The simple explanation for this fact is that majority of the audience to micro-niche websites are interested audience who are willing to spend for their interests.
5) Advertizers' Budget: There is no fixed price for ad spaces. Advertizers bid for them and each space goes to its highest bidder. If advertizers that come for an ad space generally bid lower, RPM will reduce; and vice versa.
There are several other reasons for the reduction of the RPM of your Adsence Account but the above-listed are the principal reasons. Based on these identifiable reasons, you can begin to make amends especially on those that are within your control and then wait a bit and have your RPM re-appreciate.