In 1968, Gulf+Western had already figured out how to co-opt the counterculture

I have a somewhat higher opinion of Lindsay Anderson than Kael (though it's been a long time since I've seen any of his movies), but this opening to her review of If.... is both fascinating and prescient. 

PR has been a big part of the film industry since the silent days, but the modern, data-driven/demographics based approach seems to date back to the post-war era (with a big dose of McLuhan coming in at the end). Kael probably the first critic to understand the full extent of how the changes in the business of motion pictures. She would explore the subject in depth in "the Numbers," particularly focusing on the role conglomerates were coming to play. (Note how even in '68 she goes out of her way to point out that Paramount is a subsidiary of Gulf & Western.)

The work of a PR flack has not changed that much over the past fifty years, but the scale certainly has. Tens of billions have been spent recently on marketing and PR. With the advent of Netflix, buzz often crowds out other metrics as the primary measure of success. That show may not have many viewers but look how many people are talking about it.

IF…. (1968): SCHOOL DAYS, SCHOOL DAYS – Review by Pauline Kael
From the advance rave quotes, I gather that many reviewers believe that If . . . . will be a great success with youth and that it is a masterpiece. One may suspect that in some cases the evaluation is based on the prediction. I think If . . . . will be a success, but I think it’s far from a masterpiece, and I should like to make this distinction, because so many people are beginning to treat “youth” as the ultimate judge — as a collective Tolstoyan clean old peasant. They want to be on the side of youth; they’re afraid of youth. (And this is not irrelevant to the subject of If . . . .) If they can be pushed by clever publicity into thinking “youth” will respond to a movie, they are then instrumental in getting “youth” to respond to it. Movie companies are using computerized demographic studies and market research to figure out how to promote movies. Here, taken from Variety, is the report on the technique adjudged most suitable for If . . . . by the same new “scientific” group at Paramount Pictures (a subsidiary of Gulf & Western) who worked out how to sell Zeffirelli’s Romeo and Juliet. The report predicted that If . . . . will repeat its British success in the United States “if it is given the same kind of intensive marketing support that made it such a hit in its premiere engage­ment in London,” and described the key element as “a very extensive screening program for critics, writers, radio and TV commentators, educators, and members of government,” continuing, “We went out of our way to pursue every means of reaching the public through newspaper editorials, radio and television panels or discussions, magazine features and lectures before important opinion-making groups. The outpouring of ‘breaks’ in all communication media was phenomenal and most unusual in that [the film] was treated as a news event away from the usual coverage of motion pictures.” It’s easy to recognize the standard advertising campaign aimed at the mass audience-— the big ads and the appearances of stars and movie­makers on the TV talk shows — but we are still novices when it comes to an advertising campaign that feeds the appetite of the media for something new and exciting, and we may not spot techniques directed at the selective, educated audience. Obviously, these techniques couldn’t work if the film didn’t have something in it for people to react to, but if it does, the publicity people can build up a general impression of urgent, clamorous response. It’s no accident when all those rave reviews come out before a picture has opened; the early reviewers get the taste of triumph as they rush to be the first to jump on the bandwagon. And when this atmosphere of consensus about the importance of a picture is built up, anybody who doesn’t go along begins to seem “out of it” — “not with it.” If . . . . has been so well sold that people were discussing it in the Village Voice weeks before it opened; that’s real marketing, and it means that the whole underground press has been alerted by now. “Youth” will “discover” another movie; in a flash forward, one can already hear the discussions on WBAI. Once this process has begun to work and the publicity has caught on, the film is important; people want to see it because they are hearing about it wherever they go. The publicity men have manufactured “news,” and the mass media don’t want to be scooped and left behind.