Member since is the date shown on an Upwork agency or freelancer profile recording when the account was created on Upwork, which fixes how many years the profile's lifetime figures have been accumulating over.
Upwork prints the date on every public profile, and unlike most of the page it cannot be edited: it is the day the account was opened. For an agency it is the date the agency profile was created, not the date the owner joined Upwork and not the year the business was founded, which is a separate self-declared field on the same page.
On its own the date says little; what matters is what it divides. Total earned over the years since the member-since date is the agency's average throughput for its whole life, and an agency with $500,000 earned since 2014 is a far slower business than one with the same total since 2022. Clients read it the other way round too: a long history with a small total is a warning, and a short history with a large total is either a success story or a client base brought over from elsewhere.
The usual misreading is to treat it as experience. An agency created last year may be a twenty-year-old firm that has only just come to Upwork, and the work history on the profile is the better guide to that.
How Upwork Insights uses it
Upwork Insights reads the date from each of the 28,921 agency pages it indexes and shows it on the agency's page as "On Upwork since" and uses it for lifetime pace: total earned divided by the years between member-since and the observation, a floor on historical throughput, as set out in the methodology. When a measured run-rate exists, the momentum component of the Index Score compares it with that pace, so account age shapes 15 of the 100 points. The valuation tool also uses years on Upwork as one of its adjustments.