Before you open PhonePe or Google Pay, take a guess.

Leave out rent and EMIs. Just everything else you paid through UPI in the last seven days: the coffee, the auto, lunch, Zepto order, your share of a dinner, and the random ₹180 you sent and forgot about five minutes later.

Ten years ago you wouldn't have needed to guess. You'd have opened your wallet and seen that ₹2,000 had become ₹600.

Today almost none of that money is something you can see.

About 55 crore users have been onboarded, and a Finance Ministry evaluation released in February found that 65% of the UPI users it surveyed make multiple digital transactions every day.

It's one of the best things India has built. But I don't think we talk enough about what happens to spending when paying becomes this easy.

Behavioural economists have a name for the small discomfort you feel when money leaves you: the "pain of paying." How strongly you feel it depends a lot on how you pay.

This year, researchers ran the cash-versus-card test at a much larger scale: 32,371 people, 65 products and 57 different prices.

Cash still hurt more to spend, even for people who carry multiple cards and digital wallets. And the difference showed up more clearly in how much people spent than in how much they were willing to pay.

Which made me think about the most boring feature cash ever had. You had to hand it over, and your wallet got thinner every time you did. One glance told you how much was left.

Digital payments removed that interruption almost completely. That was the whole idea, and it worked.

The strongest Indian evidence I found comes from demonetisation. In November 2016, millions of people who relied on cash were pushed into digital payments overnight.

Researchers can rarely create that on their own: a huge group of people switching how they pay for reasons that have nothing to do with wanting to spend more.

NUS's Sumit Agarwal, IIM Bangalore's Pulak Ghosh and two colleagues studied transaction data from nearly 925,000 shoppers at a large Indian supermarket chain.

The shoppers who had depended most on cash moved most heavily to digital payments, and they started spending more.

When cash came back, the extra spending stayed.

The researchers checked the obvious alternatives: income shocks, price changes, easier credit, purchases simply moving into the supermarket from somewhere else.

None of them explained it.

There's one more detail: according to a summary of the study by the National University of Singapore, shoppers who switched to digital were more likely to buy temptation goods like tobacco and fizzy drinks.

The researchers' explanation is simple. When cash leaves your hand, you feel the loss. When a number changes on a screen, you feel it a lot less.

For decades, "pain of paying" was a very good metaphor. This year, a team including INSEAD's Hilke Plassmann tested whether it's literal.

It wasn't the same as physical pain. When participants paid with electric shocks instead of money, the brain's physical pain areas lit up as well. Money only touched the emotional side.

So losing ₹2,000 isn't something only your Excel sheet dislikes. Part of your brain registers it as a small hurt.

And we've spent the last decade making that moment as smooth as possible.

Scan, amount, PIN, done.

Half the time I'm out of the shop before the notification arrives.

I don't miss ATM queues or hunting for change. UPI is faster, often safer and easier for merchants.

But cash was doing one useful thing by accident: it made spending noticeable. UPI won't do that for you, so you have to do it yourself.

₹180 still costs ₹180, even when paying for it takes three seconds.

Hit reply and tell me: before you checked, how close was your guess for the last seven days?

I read every email.

Until next week,
Ritesh

P.S. If your guess was within ₹1,000, reply and tell me how. I'd like to know :)