The role of the chief of staff (COS) has been growing in importance and popularity as the pressure on leaders in both the private and public sectors intensifies, explains McKinsey’s analysts in their latest article. So who exactly is a COS?

These individuals are asked to “spearhead transformational change, navigate complex business dynamics, balance strategic and tactical priorities, and handle myriad additional tasks. CEOs and other senior executives need to ensure that their own offices function seamlessly. Enter the chief of staff (COS).”

The analysts developed an empirical picture of the COS role by analysing publicly available data on approximately 250 chiefs of staff who have served in the role within the past eight years.

The research group is nearly evenly divided between men and women, with its members having experience across approximately 300 global organisations. The analysis reveals significant variation in COS career paths and responsibilities, yet “a few common archetypes begin to emerge,” wrote the analysts.

First question: How to hire a COS?

According to McKinsey, nearly two-thirds of chiefs of staff are promoted from within their organisations, which highlights the importance of a COS possessing deep institutional knowledge and strong internal networks to ensure they can be effective from the outset. This trend is even more pronounced in large organisations: at companies with 50,000 or more employees, 80% of the COS are internal hires.

When organisations do recruit externally, they often look beyond their own industries, with over three-quarters of these hires coming from other sectors. McKinsey notes that this is not surprising given competitive concerns, but it also underscores that many chiefs of staff use the role as an opportunity to pivot their career direction.

“Our analysis indicates comparable performance between internal and external hires. While organisational knowledge is valuable, other skills—such as the ability to influence, build relationships, and bring fresh perspectives—are equally important,” explain the analysts. For example, one COS might climb the ranks within the company, while another joins the organisation at the same time as the CEO; both have been highly successful in their roles.

Second question: How much professional experience must they have?

The average COS has around 12 years of experience, progressing from mid-level to senior roles. However, in larger organisations, chiefs of staff to senior executives generally have more years of experience. This trend aligns with larger companies’ preference for internal hires, reflecting principals’ desire to work with COSs who understand internal processes and can effectively navigate the complexities inherent in large organisations.

Typically, COSs join from positions such as senior managers and move towards one of two career paths. The first type of COS remains in the role for five to ten years, focusing on administrative tasks, such as supporting corporate governance (such as  tracking KPIs or preparing for board meetings) and managing projects run from the principal’s office.

The second group consists of mid-career executives with ten to twenty years of experience. In this case, their roles tend to encompass a greater level of leadership, and they often serve as their principals’ proxies in discussions and decisions.

Third question: Who does the COS serve?

Recently more senior executives in both public and private sectors have been hiring COS to manage their office’s operations. 

“Approximately three-quarters of chiefs of staff in our sample support CEOs, while the rest serve other C-suite executives, regional managing directors, or board chairs,” wrote McKinsey’s analysts. 

In some organisations, different COS tend to work together when multiple executives within that organisation  have chiefs of staff. There, they share best practices, and coordinate their principals’ shared priorities. 

In other cases, including some of the world’s largest companies, there are formal COS programs, with most senior-executive team members assigned chiefs of staff and individuals sometimes playing multiple COS roles during their careers at those companies, writes McKinsey.