The chief obstacle standing between CHROs and a straight-line move to the top job is lack of P&L experience.

Human resources executives have long been familiar with “glass ceilings” – the invisible employment barriers that prevent a class of people from rising higher. But what about the ceiling for CHROs themselves? Few serve as independent directors on boards; almost none go from the top HR job to the CEO chair.

Meanwhile, C-level heads of other functions – finance, sales & marketing, operations – routinely make the jump to CEO and often serve on external boards. And the list of functions from which directors and CEOs might be drawn is steadily expanding. Think CIOs.

The chief obstacle standing between CHROs and a straight-line move to the top job is lack of P&L experience. While some companies have made HR a stop on the development path for high-potential business leaders, few offer equivalent opportunities for promising HR leaders to develop their business skills.

Because such opportunities for top HR executives are rare and the requirement for such experience unlikely to change, serving on boards appears to be the more promising route for ambitious CHROs.

Such service for CHROs certainly makes sense as talent has become the issue for many companies: attracting it, developing it, retaining it, and turning it into a decisive differentiator. As someone who works at the intersection of people, processes, and strategy, an outstanding CHRO offers a perspective on talent issues that many boards could use.