Avg. monthly searches metric should reflect the average the number of searches for the term over a 12-month period (source).
But the returned average is quite often too low to really be accurate. For example when I go to Google's keyword planner and enter a moderately popular search term such as
cron expression generator the result indicates that the average monthly search volume lies somewhere between 1K to 10K per month.
But when I Google the same term and then look at the average monthly visits of the first few websites on similarweb.com, the numbers just don't add up. For instance the website crontab.guru, a popular cron expression generator, gets about 605K monthly average visits according to similarweb. I can imagine that a good amount of those visits come from people who first searched for 'cron expression generator' on Google. Other cron generator websites also have a lot more monthly visits then 1K to 10K.
trends.google.com shows that the trend score for
cron expression generator is actually quite high (region was set to worldwide and period to 12 months). So why does keyword planner return such a low estimate for this keyword group? How should the average monthly search estimate be interpreted?