How future flight fares are gathered by Google flights? [duplicate]

I have checked Google Flights and many other online OTAs, displaying flight fares for future dates (extending upto 1 year). How are these rates decided and from where these data come? Are these rates predicted by respective OTA, or they come from any GDS (Global Distribution System) by airlines themselves?

Also whether these rates change with time? I mean if I book a flight ticket today (18th April, 2019) for the departure at (11th August, 2019) in $100, then will this price of 11th August, 2019 departure, for same flight, remain same for all the days there after till 11th August, 2019?

Example of Google Flight calendar with flight fares:

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Why are flights cheaper through Google?

Doesn't always have the lowest fares: Google Flights works by searching fares sold directly from the airlines and a handful of the top online travel agencies (OTAs), such as Expedia or Orbitz. Many times the best fares are found on smaller online travel agencies that Google Flights doesn't look at.

Do airlines raise fares while you search?

However, airlines say prices change not because of a consumer's search history on a website, or their cookies, but because of inventory updates or glitches on the website, FareCompare's Rick Seaney said in an email.

Do flight prices change based on web browser?

Surprisingly, there is very little evidence that online travel sites are raising prices the more that you search for a specific trip. In fact, they tend to show lower prices to logged-in users.

Do airlines add more flights as the date gets closer?

Specifically, plane tickets usually don't get cheaper closer to the departure date. Instead, flights tend to be the most inexpensive when you book between four months and three weeks before your departure date. According to the CheapAir.com 2019 Annual Airfare Study, you can expect rates to go up after that period.

How to find the cheapest fare of any Airlines | Google Flights | Gaurav Gera

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