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FAST COMPANY/THE CRITICAL YEARS THAT SHAPED LEADERSHIP

01 December 2025

Whether they are owners, CEOs, or senior executives, there are differing evaluations regarding the specific periods and years that shape the styles of successful leaders. Research by PROF. ERIN MEYER of INSEAD is one such study. However, leaders from TURKEY express views on this subject that differ from what the research suggests.

The famous author BUKET UZUNER, in her novel 'SU' (Water), included sentences that received great interest from readers, especially teachers: "The world's greatest miracle is encountering a good teacher when you are very young. Other miracles beyond this exist only in holy books." In later years, BUKET UZUNER would say, "There were readers who asked where I got this epigram, as well as many teachers who sent thank-you letters. No, I did not quote this from anywhere. This was a result naturally distilled from my own experiences and what I have learned."

LEVENT KÖMÜR, CEO OF ULUDAĞ İÇECEK, recalled BUKET UZUNER’S words from the novel 'SU' while sharing the most important period that shaped his leadership. KÖMÜR evaluated: "The years that shaped my leadership are the years I worked with very good teachers and leaders. In other words, it is not a specific year or period, but the people who had an impact on me."

PROF. ERIN MEYER from INSEAD, one of the world's leading names in corporate culture, produced a response to BUKET UZUNER’S evaluation from a different geography through research aimed at revealing the periods/years that shape leaders. The study, covering 1,800 leaders from numerous countries, sought an answer to the question: "Which year shaped your leadership/business style?"

PROF. MEYER summarized the message emerging from the responses: "Some pointed to childhood and early youth. However, the majority's choice was the first 10-15 years of their career life." Highlighting the importance of the early period of professional life in terms of leadership and business culture, PROF. ERIN MEYER added: "The early period of one's 20s is like a sponge. During this time, you learn how to communicate and what is considered professional. The first dozen pieces of feedback you receive have a major impact on your future leadership. By the time you reach age 35, your habits are already deeply rooted."

The results of the survey conducted by PROF. MEYER with 1,800 people reveal the most important period on the road to success:

  • 51% Early Career Period
  • 22% Country of Residence
  • 11% Between Ages 10-15
  • 16% First 6 Years of Life

ONUR YAPRAK, GENERAL MANAGER OF BAYER TURKEY, points to a timeframe that encompasses the framework drawn by ERIN MEYER and shares that two periods shaped his life: "First is the 4-year high school period I spent at the NAVAL HIGH SCHOOL. Here, I started high school at age 14, responsible for leading a team of 30 people. I had the chance to experience concepts like taking responsibility, task distribution, and delegation at a childhood age. The second important period was when I worked as a brand manager at P&G. There, while making many important decisions for multi-million dollar brands, I learned how vital it is to achieve results by collaborating within a matrix structure."

PROF. MEYER considers the first 10 years of a career to be very critical. She shares that during this period, "professional habits are formed, communication patterns are established, and 'collaboration styles' are shaped." She states, "Every period is important, but those that leave the deepest marks in business life are the early years of professionalism."

BAHAR UÇANLAR, GENERAL MANAGER OF DIAGEO TURKEY, points to exactly such a period: "In my career journey and approach to life, I have tried to learn something from every experience. Even situations that seemed difficult or negative added a lot to me over time," she says, sharing her core approach and adding:

"I can say that the period that most shaped my leadership was when I went to the USA for my master's degree and my first job there. I believe my career process at BAIN, one of the country's largest management consultancy firms, stands out in particular."

According to UÇANLAR, this process developed her abilities such as looking at events from the outside and structural thinking; it also provided a strategic perspective. She finds the people she met, their kindness, and the experiences she gained very valuable: "These years had a great impact on my leadership during the period when I returned to TURKEY and especially transitioned into marketing."

American psychologist PROF. MEG JAY points out that an average person makes 80% of the critical decisions in their life before the age of 35. Therefore, she underlines that the 20s and 30s shape "leadership." Some studies reveal that leadership is 70% shaped during one's 30s.

SANİ ŞENER, CHAIRMAN OF TAV CONSTRUCTION, says, "My leadership was not shaped by a single period, but by every experience I lived." He draws attention to experiences gained and people known rather than a single timeframe: "Of course, I built my leadership on successes, but I experienced the greatest growth through my failures. I learned from every mistake I made; they were like leadership lessons to me. I also learned this from my experiences: the highest rank a person can achieve throughout their entire life is to be trustworthy."

MUHTAR KENT (Former CEO of COCA COLA): "The subject of leadership is not seasonal; it cannot be tied to specific years. Effective and lasting leadership develops and strengthens in every period. Effective leaders succeed in developing themselves by being open to innovations in every period and staying ahead of rapidly changing conditions. Everyone—small or large, young or adult, regardless of country or company—always needs to grow. Individually, 'growing' means being open to innovations and staying ahead of changes."