Sign of the Times was conceived in early October when I started to see what I perceived as a greater number of homeless people in New York City. As a native New Yorker, it surprised me because I had never seen so many people begging and sleeping on the streets. It occurred to me to start buying the signs that the homeless use to ask for money.

I immersed myself in the project, going out almost on a daily basis and walking five, six, seven hours a day. Once, I even walked 12 hours around the city – uptown to Harlem, East and West, downtown to Battery Park and back home to the East Village. I never took transportation anywhere because I felt that since the homeless live on the streets, I had to walk the streets like they do. After a while, a few said to me, "I've heard of you. You're the guy going around buying signs. I was wondering if you were ever going to find me." I bought about 200 signs and usually offered $20 which they were happy, even ecstatic, to get. (Once, though, I saw a sign that said, "Just need $10". So I said to the guy, "I'll give you $10 for it" and he said, "You got it. I guess the sign did its job!")

What struck me about the people who sold me their signs was their willingness to let go of them. It was as if they had little attachment to them even though some signs had been with them for a long time. Of course, they needed the money. Many people would tell me they had made nothing that day. But I also think that those who possess little have less attachment to material things. They know what it's like to live with less.

I had a certain way of approaching people. Whenever I saw anyone sitting on the street with a sign I wanted, I would crouch down, but not sit down. To sit down next to them would be like sitting on their couch without asking permission. But by crouching down, I could look them in the eye and be on the same level. Then I would say, "Can I ask you a question?"

They always said yes and I'd say, "I'm an artist. And artists see things in a different way. And one of the things I see are the signs the homeless have. I'm buying these signs because I see every sign as a story. There are many stories out here that should be heard. Can I offer you $20 for your sign?" They would all say yes, and it touched me how grateful many people were when I bought their sign. I got several hugs and many a "God bless you."

I bought signs from people of all ages, including some who were my age. I remember buying a sign from a man in his 60s who was sitting outside the McDonald's around 10pm. He looked at me as if I was an angel from heaven. He had pennies in his cup and couldn't believe I wanted to give him $20 for his sign. He said, "Now, I can get a bed and a meal."

The youngest person I bought a sign from was probably 16. I forgot to ask her age, but she could have been even younger. Her sign read:

Mom told us to wait right here. That was 10 years ago.

I got every sign I wanted except one. It was a nice sign, with a photograph on a small button and some other details and writing. I had just bought a sign from a friend of this sign's owner, but when I asked to buy this sign, the man holding it explained that it was his lucky sign. He'd had it for five years. I said, "OK" and walked away. I could have offered more money, but I didn't want to take his lucky sign away from him.

My funniest encounter, the one that always makes me smile, was the time I approached two guys who were slouched over, deep asleep in the afternoon. These guys were out cold when I say to one of them, "Hey mister, can I talk to you?" I'm crouching next to him on the sidewalk and he doesn't respond, so I nudge his hand, which is sticking out over his knee, and I say, "Hey, mister, I want to talk to you."

He doesn't move but waves his hand, shooing me away. So I say to him, "Listen, I want to buy something." His head is covered in a hood and he says to me without looking up, "I've got nothing to sell." "Your sign", I say. "I want to buy your sign." All of a sudden he jumps out of his slumber smiling, as if he'd been called to a board meeting to make a deal. What I love is that it never occurred to him he had something someone wanted to buy.

I won't say Sign of the Times is a political piece, because if it is, whose politics? Mine or those of the people I encountered? But it's a timely piece, marking the end of Mayor Bloomberg's term. It's the mayor's parting shot, what he left us with. Ironically, many people do not see a homeless problem. They are too busy going about their business to see the people lying at their feet. But I believe the homeless have influenced New Yorkers in at least one way: they've made sitting on the streets acceptable. On several occasions I approached someone sitting on the street only to discover it was a student or tourist looking at an iPhone or at the people walking by as if they were sitting at home watching television.

Sign of the Times is a reaction to a social injustice and tragedy. It's a testimony to the homeless men and women who roam the streets in search of food and shelter. It's also a chronicle of the times we live in. A few days ago I went to Paris for an exhibition of mine. I was immediately struck by all the people I saw on the streets of Paris. I have been to Paris more than 20 times and have never seen so many homeless in the City of Love. I easily could have done this project in Paris.

Although the homeless are at the bottom of the economic ladder, many Americans are not far from it. They may not be homeless, but they're poor. Fifty million or more Americans live at or below the poverty line.

I call this piece a collection because that's what it is, a collection, and I'm the collector. But I'm also an artist, and I've made my collection a work of art. It's a voice, an instrument, mine and theirs, telling a story that needs to be heard. It's the story of the poor in New York City, in America and in the world.

• This piece was published on 18 December 2013 on Creative Time Reports, part of the Guardian Comment Network.