Obama had committed to reading 10 letters a day when he first took office, becoming the first president to put such a deliberate focus on constituent correspon­dence. Late each afternoon, around five o’clock, a selection would be sent up from the post room to the Oval Office. The “10 LADs”, as they came to be known – for “10 letters a day” – would circulate among senior staff and the stack would be added to the back of the briefing book the president took with him to the resi­dence each night. He answered some by hand and wrote notes on others for the writing team to answer, and on some he scribbled “save”.

Starting in 2010, all physical mail was scanned and preserved. From 2011, every word of every email fac­tored into the creation of a daily word cloud, dis­tri­buted around the White House so policy makers and staff members alike could get a glimpse of the issues and ideas constituents had on their minds.

In 2009, Natoma Canfield, a cancer survivor from Medina, Ohio, wrote in, detailing her staggering health insurance premiums in a letter Obama framed and had hung in a corridor between his private study and the Oval Office: “I need your health reform bill to help me!!! I simply can no longer afford to pay for my health care costs!!” It stood in for the tens of thousands of similar letters he got on the healthcare issue alone. They saw spikes in volume after major events such as the mass shootings in Newtown, Connecticut, and Charleston, South Carolina; the Paris terrorist attacks; the government shutdown; Benghazi. You could see these spikes in the word clouds. “Jobs” might grow for a time, or “Syria”, or “Trayvon”, or a cluster such as “family-children-fear” or “work-loans-student” or “Isis-money-war” surrounding a giant “help” – the most common word of all.
...
“I think I understood that if somebody writes a letter and they get any kind of response, that there’s a sense of ... being heard,” he said. “And so often, espe­ci­ally back in 2009, 2010, 2011, a lot of people were going through a lot of hardship. And a lot of them felt alone in that hardship. They were losing their homes, or they’re dealing with somebody at the bank and the bank say­ing: ‘There’s nothing we can do. You’re going to lose your house.’ Or they’ve got a pink slip, and they’ve lost their job, and they’re going to interview after interview after interview. Over time, I think it’s easy for folks to feel a little invisible, as if nobody’s paying attention. And so I did, I think, understand that if I could at least let them know that I saw them and I heard them, maybe they’d feel a little bit less lonely in those struggles.

https://www.theguardian.com/books/ng-interactive/2018/aug/18/barack-obama-reveals-how-letters-from-the-american-people-shaped-his-presidency-interview