How Harnessing Data Created a $1bn Swing in MLB’s Favor with Jonathan Mariner


Jonathan Mariner has held a number of unique roles within the scope of his financial career, most notably as Chief Financial Officer with Major League Baseball – where he transformed the league’s financial outlook with a sophisticated data-led approach.

Jonathan is also the founder and president of TaxDay – a travel-tracking app for tax purposes, built for residents who work or reside in multiple states.

Jonathan has a huge amount of knowledge and insight to share, and he did just that in a stellar conversation with Jason Dorsey for episode two of our brand-new podcast series, Leading with Data.

Hit play on the player above or read on to find out more.

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Transforming MLB’s Financial Position

Jonathan originally aspired to be an accountant and studied accountancy at university. He was all set on the path to becoming an accountant until he decided to go to Harvard Business School.  A course at Harvard called ‘Accounting: The Language of Business’ opened his eyes and shaped his view of business; it was about how data drives decisions.

He spent a lot of his career in corporate strategy and planning roles before moving into the sports industry, having served as the CFO for Florida Marlins before moving to Major League Baseball.

Jonathan’s achievements at MLB cannot be overstated. He transformed the league from a loss-making behemoth into a profitable, thriving business – to the tune of a $1bn recovery in just five years.

So, how did he achieve it and what role did data play in this dramatic transformation?

Well, Jonathan joined them in 2002 and soon after that, he helped to implement a new collective bargaining agreement. One of the things that they put in place with the agreement was a new way to control how teams control their debt level.

At the time Jonathan joined MLB, the financial position was not healthy. Out of 30 teams, only three of them were actually making any money.

The reason I got that collective bargaining agreement done was that we needed to change the economic system… The future of the league was resting on being able to turn this thing around financially.”

Teams had three years to comply with the new rules, and in order to track this, they needed data.

Jonathan hired an innovative tech start-up that helped the league build out a financial reporting system that allowed teams to do three things:

  • Report their data to the league in a consistent format
  • Forecast their financial performance
  • Have a separate revenue sharing step

Out of the three features, forecasting was so critical because it meant the league could share data that allowed everyone to see where the team was headed from a business perspective. Within five years, the team went from having a half-billion-dollar consolidated loss operating income to a half-billion-dollar positive.

Impressive results were only made possible by getting to grips with the huge amounts of financial data that existed within the league but had, until then, gone untouched.


How and Why Jonathan Founded TaxDay

Being audited by New York State was not an enjoyable experience for Jonathan, but it merged quite well with his move away from MB.

Working and living across states meant Jonathan had a huge headache on his hands when it came to his taxes. So, Jonathan set his sights on building an app. He wanted to build a system that would help people like him document where they were and to prove their finances with receipts. From this problem, the seed of TaxDay was planted.

I wrote an outline of what it would entail. I reached out to a company that done another big data project for me at MLB early in my career there and we decided to launch the TaxDay app.”

And so, from an idea scribbled onto a few pages, Jonathan and his team created a brilliant app that utilizes data in a way that simplifies a laborious task.


Data Will Become Ubiquitous

When pondering the future of data, Jonathan thinks that that data will become universal. Google, Siri, Alexa…they are just the tip of the iceberg, and we take them for granted.

However, the information is always out there – it’s about analyzing the data and delivering it to people. As machine learning and data processing become much more efficient, the information will be at everyone’s fingertips in a much more ubiquitous way than it is today. Data is going to become more and more ever-present.


Advice for People Early in Their Careers in Data

There are any number of brilliant ideas and pieces of advice we could share with you from Jonathan’s interview, but it feels appropriate to leave some career advice from a man with such a glittering resume:

I always found it useful to not only look at the job in front of me, but think where would that take me next? What’s the next move? Which direction will it take me?

If you aren’t sure which direction to head, we can heartily recommend listening to Jonathan’s full interview on the Leading with Data podcast.

That’s certainly a great starting point!


Check out the rest of the Leading with Data podcast series for more interesting insights from business leaders around the world. You can listen to the podcast on your favorite podcast app including Apple Podcasts and Spotify.