Growing up, I noticed that something happened to my father as he aged: his wallet expanded with each passing year.
There were new credit cards, membership cards, coffee cards, business cards, pictures of his family, stamps and other plastic and paper things, added almost weekly. Eventually, his wallet grew so large that he would pull it out of his back pocket when he sat down, dropping it on the table like a brick.
As I've grown older, something entirely different has happened to my wallet: each year, it has become slimmer. Things that once belonged there have gradually been siphoned out by my smartphone. Last week, I realised I didn't need to carry a wallet any more. My smartphone had replaced almost everything in it.
So, it's gone. Add that to the pile of things — my address books, Filofax, portable music player, point-and-shoot camera, printouts of maps — that have melded into the smartphone.
So where did the things that used to live in my wallet go?
Printed photos, which once came in "wallet size", have been replaced by an endless roll of snapshots on my phone. Business cards, one of the more archaic forms of communication from the past few decades, now exist as digital rap sheets that can be shared with a click or a bump.
As for cash, I rarely touch the stuff any more. Most of the time I pay for things — lunch, petrol, clothes — with a single debit card. Increasingly, there are also opportunities to skip plastic cards. At Starbucks, I often pay with my smartphone using the official Starbucks app. Other cafes and small restaurants allow people to pay with Square. You simply say your name at a register and voila, transaction complete.
But wait, what did I do with all of the other card-like things, such as my gym membership ID, discount cards, insurance cards and coupons? I simply took digital pictures of them, which I keep in a photos folder on my smartphone that is easily accessible. Many stores have apps for their customer cards, and insurance companies have apps that substitute for paper identification.
Because I own an iPhone, I don't have to carry tickets around, either. I use Passbook, a free Apple app that can store boarding passes, movie tickets, coupons and loyalty cards. I've used these digital replicas to board a flight to Los Angeles and to get into a movie and a baseball game.
Some people might cringe at the thought of putting a picture of an insurance card on their phone, but if I lose my phone, there is a password to stop someone from opening it. My wallet never came with a password.
There are a couple of things I still carry in my pocket, held together with a money clip: the debit card and my driver's licence. But I'm confident that those, too, will someday disappear.
Soon enough, my phone will become my sole credit card, and the only thing left in my pocket will be my driver's licence. And at some point, the government will enter the 21st century and offer a digital alternative for that.
Or maybe I won't need a driver's licence at all: when cars drive themselves in the not-too-distant future, I'll be taking a nap while my car takes me to work.
The New York Times