This is the first in a series of stories about the demographics of the Senior Executive Service. If you are a senior executive under the age of 40, please contact klunney@govexec.com to help us in our research.

About 4 percent of the Senior Executive Service is under the age of 40, and the majority of those young leaders are non-career appointees, according to the latest data from the Office of Personnel Management.

Unsurprisingly, the ranks of the career SES are dominated by older federal employees, while younger senior executives tend to be administration appointees, according to Fedscope data compiled by CEB, a member-based advisory company. The bulk of the total Senior Executive Service are career employees – a whopping 90 percent. Only 10 percent of SES positions governmentwide by law can be non-career appointments. There is a third SES category – limited term or limited emergency – which accounts for a small fraction of the overall total.

But of the 7,014 career senior executives working in government as of September 2014, only 1.8 percent, or 126 employees, were under the age of 40. By contrast, of the 682 non-career senior executives in government at that time, 24 percent, or 166 employees, were born in or after 1975. The Office of Personnel Management must approve any non-career appointments, which cannot exceed 25 percent of an agency’s SES position allocation.

So which Cabinet-level agencies had the most senior executives under 40? The Homeland Security Department (28), followed by the departments of Health and Human Services, Justice and Treasury, with 26 SESers each. Of the 28 SES employees under 40 at DHS, 16 were career as of September 2014 – the most of any Cabinet-level department in that category. Treasury had the most non-career SESers (17) under the age of 40.

The Air Force, Army and Navy departments employed the fewest senior executives under 40 among the biggest agencies. The Air Force and Army each boasted one, while the Navy had two. The Army’s SESer under 40 was listed as non-career, while the Air Force and Navy senior execs were in the career category.

Believe it or not, there were four senior executives between the ages of 25 and 29 – none of them career – as of September 2014. Three of them were working at Cabinet-level agencies (Commerce, DHS and Veterans Affairs) and the fourth was at the Environmental Protection Agency. It makes sense that most of the Senior Executive Service, which totaled 7,802 employees as of September 2014, skews older. After all, entrée into the elite corps is determined by career-long accomplishments that can take years to accumulate. Fifty percent of the SES can be found in one decade -- between the ages of 50 and 59.

But for years, SES advocates, including the Senior Executives Association, have worried that pay compression as well as legislative efforts to curb bonuses, will deter up-and-coming, talented employees from considering the SES. The pay of federal employees at the top of the General Schedule can overlap with certain senior executives, who are part of a different pay scale. For example, a GS-15, Step 10 in the Washington, D.C. area will earn an annual salary of $158,700 in 2015; that could be more money than an SES employee, depending on her position and pay category.

It’s tough to convince employees to sign up for a job that is more work for the same amount, or less, pay.

Here’s how the demographics of the SES break down by age based on the Fedscope data compiled by CEB:

(Top image via jorgen mcleman/Shutterstock.com)