Could this be related to the size of the actual newspaper shrinking? As in the amount of pages? Most publications have trimmed down their size as the internet has consumed their reader base and profitability.

I wish I understood even half of what you're getting at.

I checked how many articles were published on 1 January 1974 versus 1 January 2010 as a kind of crappy way to check if maybe the disparity is due to the number of articles published, assuming the articles are roughly the same average length. I came up with 204 articles published on 1 January 1974 and 92 articles published on 1 January 2010. So we expect twice as many but instead we get 25 times. I could already tell any ratio for "yesterday" would not hold for other words but went ahead. I cannot find any data on the size of New York Times articles over the years. This remains an open question.

I think it's because back in the 1970's, people relied on news reporters to inform them what had happened (perhaps overnight or overseas) "yesterday".
As the internet became more prevalent, people were able to check on their own.
In today's culture and the advancement of things like twitter, we can personally connect with people in real time with regards to what's happened. We already know what happened yesterday, we know immediately what's happening today, and we're getting briefed on what's expected to happen tomorrow.
"Your emotional state is not my responsibility." – Warren Smith

Okay then.
MAGA! FAFO! Schrodinger's Cat walks into a bar, and doesn't. Dumbocraps: evil people who celebrate murder.

I think it shows the things that were important at certain times and how they ebbed and flowed. You can see the growth of the internet or the rise of China or the decline of the VCR in the public consciousness, interesting things like that.

So it this supposed to prove something?
MAGA! FAFO! Schrodinger's Cat walks into a bar, and doesn't. Dumbocraps: evil people who celebrate murder.

yesterday, today, tomorrow — they're bolded in the images.

Oh okay. What is the word?
MAGA! FAFO! Schrodinger's Cat walks into a bar, and doesn't. Dumbocraps: evil people who celebrate murder.

You have to go to the website.

I hovered over the dots, but nothing happened.
MAGA! FAFO! Schrodinger's Cat walks into a bar, and doesn't. Dumbocraps: evil people who celebrate murder.