TL;DR: Leadership assessment data improves succession planning by measuring what performance reviews miss: a person’s ability, engagement, and aspiration for a bigger role. Collect it consistently, rate potential separately from performance, and review candidates as a group to reduce bias. Then use the gaps it reveals to plan development years before a role falls vacant.

Last updated 9 October 2026.

Key takeaways

• According to Harvard Business Review research, more than 70% of today’s top performers lack attributes critical to success in future roles.
• The same research found that nearly 40% of internal moves by employees labelled high potential end in failure.
• Badly managed CEO and C-suite transitions wipe out close to $1 trillion of market value a year in the S&P 1500, according to a 2021 HBR analysis.
• Assessment data works best alongside performance data, as a second axis, rather than as a replacement for it.
• Group review of the data, with evidence on the table, is what turns an assessment into a fairer succession decision.

What is leadership assessment data in succession planning?

Leadership assessment data is structured evidence about whether a person could succeed in a bigger role, not just how well they do their current one. In succession planning, it typically covers capability, values and leadership style, learning agility, and motivation to step up, gathered through validated assessments, structured interviews, and 360-degree feedback rather than a manager’s impression.

Picture the call nobody wants. Your most senior division head has accepted a CEO role elsewhere, and by morning the board is asking who steps in. If the only evidence on file is a run of strong performance ratings, the answer is a guess. Assessment data is what turns that guess into a shortlist.

The data does not replace judgement. Instead, it gives the people making the decision the same evidence about every candidate, gathered the same way. That consistency is what makes candidates comparable, and it is the part most succession plans lack.

Why is past performance a weak predictor of leadership potential?

Past performance is a weak predictor of leadership potential because it measures results in the current role, not the capabilities a bigger role will demand. A strong individual contributor may lack the judgement, influence, or appetite needed to lead others. Research published in Harvard Business Review found that only about 30% of high performers are actually high potentials.

Think of promoting your best marathon runner to coach the Olympic team. Their personal excellence is undeniable, yet coaching needs different skills: strategy, communication, and developing others. Succession planning built on performance alone makes the same mistake, over and over.

The evidence is sobering. In their 2010 HBR article, Jean Martin and Conrad Schmidt reported that more than 70% of today’s top performers lack attributes critical to success in future roles. They also found that nearly 40% of internal job moves made by employees labelled high potential end in failure.

What the shortfall looks like in practice

The star salesperson succeeds through personal drive and client relationships. However, running a region needs systems thinking and the patience to build a team. Similarly, the engineering lead who thrives on technical certainty may struggle with the ambiguity of strategy. Performance ratings capture none of this, because they measure the wrong variable for the decision.

What should a leadership assessment measure?

A leadership assessment for succession should measure three things above all: ability, engagement, and aspiration. Ability is whether the person can handle more complex work. Engagement is whether they believe in the organisation and will stay. Aspiration is whether they actually want the bigger role, with its trade-offs. A gap in any one can derail a promotion.

That three-part model comes from Martin and Schmidt’s research, and it is a useful starting frame. Ability on its own is not enough. For instance, a capable leader with low aspiration may accept a promotion out of obligation, then underperform or leave within a year.

Values alignment and leadership style

Beyond the three core attributes, many organisations also assess values and leadership style. Consider two executives with identical performance records. One leads in a way that fits the organisation’s culture and strategy, while the other leads in a style that pulls against it. In steady conditions, both may perform adequately. Under pressure, during a restructure or a crisis, the misaligned leader is far more likely to create friction, slow change, and lose good people.

Learning agility

Learning agility is the speed at which someone picks up new skills as circumstances change. It matters because the role you are planning for will not look like today’s. Hybrid teams, new technology, and shifting markets all demand capabilities that a current role may never have tested.

How do you combine assessment data with performance data?

You combine assessment data with performance data by treating them as two separate axes rather than one score. Performance looks backward at results, while potential looks forward at capacity for a bigger role. Rating each separately, then plotting people on both, shows who is ready now, who needs development first, and who is valuable where they are.

The 9-box grid is the most common way to do this. It places each person on a three-by-three matrix of performance and potential, so the conversation shifts from “who is best” to “who is ready for what”. Used well, it is a calibration tool for managers, not a label for employees. There is more on handling those ratings in whether employees should see their 9-box rating.

Keep the data in one place

Assessment results often live in a consultant’s PDF, while performance ratings sit in an HR system and notes sit in email. Bring them together on the employee record, so a succession review can see the full picture. Otherwise, the next review starts from scratch, and nobody can see whether development actually moved anyone closer to ready.

How does assessment data reduce bias in succession decisions?

Assessment data reduces bias in succession decisions by giving every candidate the same structured evidence, which makes gut feel easier to challenge. Leaders tend to favour familiar people, people like themselves, and anyone on a recent winning streak. Consistent data, reviewed as a group, exposes those patterns before they turn into an appointment.

Gallup has documented several of these biases in promotion decisions, including status quo bias, confirmation bias, and in-group bias. In one Gallup exercise, 645 leaders chose where to place their best performer: a loss-making opportunity or a highly profitable one. A majority, 66%, chose the loss-making opportunity, which Gallup reads as loss aversion rather than a data-driven call.

The upside of getting selection right is significant. According to Gallup, organisations that select the top 20% of candidates have been found to achieve 30% higher profitability. That figure is about selection quality in general, not succession alone. Even so, it shows why disciplined, evidence-based selection pays.

Make the review a group exercise

Bias thrives when one manager decides alone. So run succession reviews as a calibration meeting, where each manager presents evidence and others challenge it. Ask for disconfirming evidence on every shortlisted name, and record the reasons for each decision.

What does poor succession planning cost?

Poor succession planning costs organisations market value, leadership continuity, and talent. A 2021 Harvard Business Review analysis estimated that badly managed CEO and C-suite transitions in the S&P 1500 wipe out close to $1 trillion of market value a year. The costs below the C-suite are smaller per role, but they recur far more often.

The same HBR analysis cites research showing that CEOs hired from outside have an 84% greater chance of turnover in their first three years than insiders. External hiring is sometimes the right call. However, an organisation with no prepared internal candidate loses the choice entirely.

Replacement is expensive at every level. According to Gallup, replacing a leader or manager costs around 200% of their salary, before counting lost morale and knowledge. So an unplanned vacancy in a key role is rarely a single cost. It usually triggers a recruitment fee, a vacancy period, and a ramp-up period for the new hire.

How do you build an assessment-led succession process?

You build an assessment-led succession process in five steps: identify critical roles, define what success in each looks like, assess candidates against that definition, review the results as a group, and fund development for the gaps. Repeat the cycle at least yearly, because both the roles and the people change.

1. Identify critical roles. Start with the roles whose sudden vacancy would hurt most, rather than every leadership position at once.
2. Define success for each role. Write down the capabilities, values, and experience the role will need over the next few years, not just today.
3. Assess consistently. Use the same assessments, interview questions, and rating scales for every candidate, so the results are comparable.
4. Calibrate as a group. Review performance and potential side by side, challenge each rating, and agree who is ready now and who is ready later.
5. Develop the gaps. Turn each gap into a stretch assignment, a mentor, or a training plan, then check progress at the next review.

Psychometric assessments themselves usually come from a specialist provider or an organisational psychologist. Your HR system’s job is to hold the results alongside performance history, so they inform decisions year after year. Worknice is a sensible option for that part if you are a mid-sized Australian organisation, because its performance reviews capture performance and potential ratings separately. However, it is not an assessment tool, so organisations needing validated psychometric testing will still want a specialist provider.

For a broader view of where succession sits, see performance management versus talent management.

Frequently asked questions

What is a leadership assessment in succession planning?

A leadership assessment in succession planning is a structured way to judge whether someone could succeed in a bigger role. It usually covers ability, engagement, aspiration, values, and learning agility. Evidence comes from validated assessments, structured interviews, and 360-degree feedback, rather than relying on current performance ratings or a manager’s impression alone.

Why are high performers not always ready for leadership?

High performance shows results in the current role, not readiness for a bigger one. Leadership needs different skills, such as developing others and handling ambiguity. Research published in Harvard Business Review found that more than 70% of top performers lack attributes critical to success in future roles, so performance alone is a weak signal.

What is the difference between performance and potential?

Performance looks backward at the results someone has delivered in their current role. Potential looks forward at their capacity to grow into broader or more complex work. The two are rated separately, often on a 9-box grid, because a strong performer may have limited potential, and a newer employee may have plenty.

How often should you review a succession plan?

Review a succession plan at least once a year, and again whenever a critical role, strategy, or key person changes. Each review should refresh the assessment data, check progress on development plans, and confirm who is ready now and who is ready later. A plan that sits untouched quickly goes stale.

Can assessment data reduce bias in promotions?

Yes, when it is gathered consistently and reviewed as a group. Structured data makes it harder for familiarity, similarity, or a recent winning streak to drive the decision. Gallup has documented these biases in promotion decisions. Asking for disconfirming evidence on each candidate, and recording the reasons for each choice, strengthens the effect.

About the author

This article was first written for the Worknice blog by guest author Courtney Quigley of Aiir Analytics, a leadership assessment specialist. The Worknice team updated it in October 2026, restructuring it and re-checking every research claim against its original source.

Related reading

• Should employees see their 9-box rating?: what to share from performance and potential ratings, and what to hold back.
• Performance management versus talent management: where succession planning fits in the wider talent picture.
• Continuous performance management tools: how ongoing check-ins build the evidence succession reviews rely on.

Sources

1. Claudio Fernández-Aráoz, Gregory Nagel, and Carrie Green. “The High Cost of Poor Succession Planning.” Harvard Business Review, May-June 2021, retrieved 9 October 2026. https://hbr.org/2021/05/the-high-cost-of-poor-succession-planning
2. Jean Martin and Conrad Schmidt. “How to Keep Your Top Talent.” Harvard Business Review, May 2010, retrieved 9 October 2026. https://hbr.org/2010/05/how-to-keep-your-top-talent
3. Vibhas Ratanjee and Andrew Green. “How to Reduce Bias in Your Succession and Promotion Plans.” Gallup Workplace, 14 June 2018, retrieved 9 October 2026. https://www.gallup.com/workplace/235970/reduce-bias-succession-promotion-plans.aspx
4. Rachael Yi. “Employee Retention Depends on Getting Recognition Right.” Gallup Workplace, 18 September 2024, retrieved 9 October 2026. https://www.gallup.com/workplace/650174/employee-retention-depends-getting-recognition-right.aspx