Advertising channels
Fig. 1. Shares of advertising sources in Google Analytics – comparison by year.
So, you're using the same tools, but their click-through and conversion rates change over time. While your overall advertising costs may remain the same, a complete change in the click-through structure can ultimately lead to less than ideal results.
Changes in traffic structure occur for a number of reasons – changes in search engine algorithms, increased click costs in advertising systems, etc.
To avoid any unpleasant surprises and understand exactly which tools you're spending your money on (and what results they're delivering), you need to set up analytics. Let's look at how to set it up step by step.

We also recommend reading the article on how to evaluate the effectiveness of an advertising campaign .
1. Analytics systems
To fully analyze advertising results, you need to install analytics systems. The easiest to manage, most common, and free are Yandex.Metrica and Google.Analytics . They install code on your website, and you access the systems through your personal account. Why do this? To track the exact origins of website traffic.