Alumni Spotlight: Louis Arranz ('15MA, Mathematics of Finance)

What is your current role?
Portfolio Manager at BlackRock, Director

What are you working on now? 
Right now, I’m managing multi-asset income portfolios at BlackRock, where I invest across global bonds, equities, and credit. I focus on identifying macro trends and relative value opportunities to generate consistent returns. The goal is to build resilient portfolios that help our clients meet their long-term financial goals.

What drew you to your field?
I've always been drawn to the intersection of math, markets, and human behavior—investing brings all three together in a dynamic, constantly evolving way. What really pulled me in though was the sense of purpose: the work we do directly impacts people’s ability to buy a home, retire comfortably, or fund their children’s education. That responsibility keeps me motivated every day.

What lessons from graduate school have you found useful in your professional life?
One of the biggest lessons from graduate school was learning how to make decisions under uncertainty—using models as a guide, but knowing their limits. It also sparked my interest in behavioral finance, especially the idea that knowing yourself is just as important as knowing the market. In investing, staying grounded and self-aware can be a real edge.

What skill has unexpectedly helped you in your career?
The ability to communicate complex ideas simply has been surprisingly important. Whether it’s explaining a trade to a colleague or helping a client understand our strategy, clear communication builds trust and alignment. In a field full of data and nuance, making things accessible is a real differentiator.

What is your favorite memory from your graduate years?
One of my favorite memories was moving from France to New York to attend Columbia. The experience wasn’t just about the world-class education, but also about connecting with people from all over the world, each with their own unique perspectives and expertise. Living at International House made it even more unforgettable. It felt like being part of a global community, all learning and growing together in the vibrant and dynamic city of New York.

What are your passions outside of your work? 
Outside of work, I’m focused on completing the World Marathon Majors, which means I’m running a bit more than I’d probably choose to—but it’s all part of the fun! I also love traveling for major sports events, where I get to combine my passion for sport with the thrill of exploring new cities, and of course, indulging in some great restaurant experiences along the way.

What is your advice for current GSAS students?
My advice for current GSAS students would be to embrace the challenges and stay curious. Graduate school is about more than just mastering the material. It’s about learning how to think critically, ask the right questions, and stay open to new ideas. And don’t forget to build relationships with your peers; the connections you make will be just as valuable as the knowledge you gain.

What is next for you, professionally or otherwise? 
Professionally, I’m focused on refining my investment strategies to navigate evolving macro trends and uncover high-conviction opportunities. The goal is to continue delivering strong, risk-adjusted returns for clients while adapting to a rapidly changing policy landscape. On a personal note, I’m dedicated to helping my son grow into a fun, curious, and well-rounded child, while enjoying the journey of parenthood and the adventures it brings.