Imagine an Olympic sport without any universal quantitative metrics. Thousands of hyper-competitive athletes competing furiously with each other, but only able to keep score by chatter at cocktail parties and compliments from their colleagues. Welcome to the world of journalism for the past several centuries.

In the age of print, circulation numbers were dubious at best and there was of course no way for anyone to tell how much a given article in a newspaper or magazine was read relative to another.

The web had the potential to change that starting in the 90s, but with rare exceptions it didn’t. While publishers could track stats like pageviews or unique visitors for every article using tools like Google (GOOG) Analytics or Omniture (ADBE), most never released granular data to the public or even their own writers. On a panel, news executives will say they don’t make stats available to staff because they don’t want their journalists writing for pageviews, but given that publishers have long been optimizing their entire online businesses for pageviews a skeptical observer might wonder if they withhold the data to keep stars from demanding raises or leaks of dismal traffic from occurring.

If journalism is a marathon, the stopwatch has just been invented. The social web now provides universal, publicly accessible, metrics on which to judge an article in the form of Twitter, Facebook (FB), LinkedIn (LNKD) and Google+ shares — let’s call them social shares.

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Social networks didn’t set out to provide this data, it’s a byproduct of their bids to get their share widgets (which feature the share count) on every webpage. The concept was popularized by Digg which encouraged publishers to put Digg buttons on article pages. As Digg faded from popularity, Facebook’s like button and Twitter’s tweet widget took center stage. It’s now became a standard social feature.

While only some publishers choose to display the social share data on their web pages, the data is available for any page on the web to anyone for free through a simple API call. It’s hard to understate how much this is changing the game of online content. Publishers no longer control some of the most important analytic data. Writers know how well their work is performing in realtime. Competitors can analyze which articles are successful or duds in rival publications. As I wrote in a prior column, public relations executives can gauge the impact of a story about their clients. Even governments can monitor (without a FISA request) the resonance a muckraking story has.

Any new metric invites a vigorous debate on how healthy it is — the value of the pageview has been hotly debated for over a decade — and the social share has its pros and cons. I’ll leave that analysis for another column. In the meantime, writers better prepare to be judged by the social share since it’s the only universal metric for articles in town.

Gregory Galant‘s the CEO of Muck Rack, the social network for journalists and companies in the news. He’s also the cocreator of the Shorty Awards which honors the best of social media. Galant advises several startups and is a mentor in the TechStars startup accelerator. Follow him on Twitter.