Comparing your Google Analytics data side by side with the dates of official algorithm updates is useful in diagnosing a site health issue or traffic drop. In the above example, a new client thought it was a switch to HTTPS and server downtime that caused the drop when it was actually the May 6, 2015, Google Quality Algorithm (originally called Phantom 2 in some circles) that caused the sudden drop in organic traffic – and the problem was probably compounded by unnatural linking practices. (This client did eventually receive a penalty for unnatural links when they ignored our advice to clean up).
The impact of SEM is immediate. SEO takes time. Through paid SEM ads, you can start to put your results in front of audiences with just a few clicks. As soon as you launch a campaign, your ads start showing in SERPs. At any time, you can turn ads on to increase visibility or turn them off to stop showing. Conversely, SEO is something that you acquire over time and typically over a long time. It can take months of implementing an SEO strategy before a brand begins to rank on search engines.
Baseline ranking assessment. You need to understand where you are now in order to accurately assess your future rankings. Keep a simple Excel sheet to start the process. Check weekly to begin. As you get more comfortable, check every 30 to 45 days. You should see improvements in website traffic, a key indicator of progress for your keywords. Some optimizers will say that rankings are dead. Yes, traffic and conversions are more important, but we use rankings as an indicator.