I wanted a simple thing: the nightly price of 5 competing hotels for every date of the next few weeks , plus which booking site sells each one cheapest. The kind of table a hotel revenue manager checks every morning.

Google Hotels already shows all of this — it just doesn't let you export it. So I scraped it. Here's what I learned, including one trap that makes most "rate calendars" useless.

The trap: Google re-ranks hotels for every date

My first attempt was the obvious one: search "hotels in Shinjuku, Tokyo" for 7 consecutive check-in dates and keep the results.

Then I checked how stable that list is. With the top 50 hotels per date over 7 dates, I got 148 different hotels — and only 3 of them appeared on all 7 dates .…