It is worth reflecting for a moment that according to the eMarketer upwardly revised figures, this is the first time the two have accounted for more than two in three of every pounds spent on digital advertising in the UK.
They came within a whisker last year, but 2019 will see the landmark figures surpassed as the two companies line up to hit a 70% share by 2021.
This is obviously not great news for the UK market. Two powerful players is not the end of the world, and it can be argued that budget is invested in them because it creates value for advertisers. However, very few people, other than the company's shareholders, would suggest this is beneficial to the UK market to have two such powerful businesses over whom there are serious question marks over privacy and tax arrangements.
That point aside, it is worth considering the reason why eMarketer researchers say they have increased this year's forecast to take up over a two-thirds share. There are two fairly obvious reasons -- concerned advertisers and GDPR.
As the argument goes, British advertisers are very wary about getting the most out of their budgets in a time when consumers are feeling increasingly concerned about making purchases, particularly big-ticket items.
Nobody knows what is happening with Brexit and what it will mean for their employment prospects, and so advertisers are prioritising reaching this concerned customer base on familiar sites. In a time of economic certainty, it would appear, advertisers' appetite to experiment with unfamiliar channels is diminished.
The case for Google search, in particular -- and highly targeted campaigns on Facebook, which can also find business "look-a-like" audiences -- has been made well over the past few years. Advertisers know the channels well. They are trusted and familiar.
Secondly -- and I think this is an interesting point -- there is the issue of first-party data being king, since the introduction of GDPR nearly a year and a half ago. Advertisers know they need to wean themselves off third party cookies.
Browsers are already beginning to do this for them, as is "Sign in with Apple" and the upcoming ePrivacy Directive.
So the duopoly was already dominant. They have had their hand strengthened by Brexit uncertainty and a move to value advertising partners who can hone audiences down into key customer segments through first-party data insights.
This move to first-party data will only deepen as the option of third-party cookies diminishes as files are blocked at the browser level and traffic is increasingly dominated by mobile devices.
I think very few people would suggest Brexit uncertainty is going anywhere too. Good news for the duopoly -- but for anyone wanting more competition in the market, the news is a little more bleak.