This was done to cut down on bots, scammers and the like. You may remember that Valve instated a policy around that time that restricts users who have not spent at least $5 from trading, sending friend invites, or using the market. Old spend only shows the money spent up before April 17, 2015.

The total spend takes into account money taken directly out of your card, as well as Steam Wallet funds which you spent on the platform. This does not take into account games purchased outside of Steam that you redeemed on Steam, only things you actually paid Valve for. Total spend is a tally of all the money you spent on Steam, whether that's buying games for yourself, gifting them to others, or buying anything off the Steam Market. It categories your spending under three main stats: total spend, old spend, and PW spend.

Or, go to Support > My Account > Data Related to Your Steam Account > External Funds Used. The External Funds page is part of the Steam Support site, so you'll need to log in to see it. There is now a page on Steam with a simple job: to tell you how much money you've spent on Steam since creating your account.

Steam market