10,000 Hours to Mastery: How Experts Are Built – and Why 20 Years of Experience Do Not Necessarily Make a Great Accountant

Where did the “ten years” idea come from?

There is an extraordinarily attractive idea about professional mastery: devote 10,000 hours to something and you will become an expert.

Under a standard working schedule, the number sounds almost mystical. Ten thousand hours amount to roughly five years of full-time work, or about a decade of intensive learning and practice.

The idea is simple enough to remember, optimistic enough to inspire, and scientific-sounding enough to be repeated in books, lectures, business seminars and social media.

The real story is much more interesting. It matters particularly in professions such as accounting, tax advisory and auditing, where someone can perform the same type of work for twenty years without necessarily developing professionally for the last fifteen.

One of the most influential lines of research came from chess. In 1973, William G. Chase and future Nobel laureate Herbert A. Simon published Perception in Chess. A strong chess player does not simply appear to have “more memory.” The expert perceives the position differently.

This led to the concept of chunking: organizing many separate elements into larger meaningful structures. When chess pieces are arranged randomly so that the position no longer has chess meaning, much of the experts’ memory advantage disappears. Their advantage therefore depends on domain-specific knowledge structures rather than a generic photographic memory.

Anders Ericsson and the rise of deliberate practice

In 1993, psychologist K. Anders Ericsson, together with Ralf Krampe and Clemens Tesch-Römer, published one of the most influential papers in the field: The Role of Deliberate Practice in the Acquisition of Expert Performance.

Among the participants were young violinists at a music academy in Berlin. By around age twenty, the highest-rated group had accumulated, on average, approximately 10,000 hours of practice.

The broader idea is much closer to: high expertise usually requires years of systematic work than to: “Anyone who practices for 10,000 hours becomes an expert.”

Then Malcolm Gladwell enters the story

In 2008, Malcolm Gladwell published Outliers: The Story of Success and popularized what became known as The 10,000-Hour Rule. Stories about The Beatles and Bill Gates transformed a complex scientific idea into an unforgettable rule of thumb.

Ericsson later distanced himself from overly simplified interpretations. His core message was never the magic number. It was the type of practice.

Not just practice – deliberate practice

Deliberate practice refers to structured effort specifically designed to improve performance.

Working for eight hours does not mean you practiced for eight hours. Repeating something a thousand times does not necessarily mean you became better at it.

What does expertise look like in the real world?

Science also challenged stronger versions of Ericsson’s theory

In 2014, Brooke Macnamara, David Hambrick and Frederick Oswald published a large meta-analysis in Psychological Science. Their analysis estimated that deliberate practice accounted for approximately 26% of variance in performance in games, 21% in music, 18% in sports, 4% in education and less than 1% in the professions included in their analysis.

These findings do not mean that practice is unimportant. They mean that human expertise cannot be reduced to a single factor. Education, prior knowledge, cognitive abilities, training quality, motivation, task characteristics, work environment, access to difficult cases, mentoring, feedback and individual differences may all matter.

Ericsson and Kyle Harwell later argued that some critical studies used definitions of deliberate practice that were broader than the original concept. The disagreement itself is useful because it shifts the conversation away from the magic number and toward the better question: what kind of practice actually changes capability?

So what is one hour of experience actually worth?

Two people may each have 10,000 hours of professional experience while the value of those hours is entirely different.

Accounting and auditing also have their own research literature on professional expertise. Studies suggest that experts may possess differently organized knowledge and, in some situations, use different decision processes.

Tacit knowledge: knowledge that is difficult to put into a textbook

Experienced professionals also develop tacit knowledge: knowledge that is difficult to formalize completely.

The expert does not know every answer

In complex professions, expertise often does not mean knowing the answer immediately. It means knowing:

• what the real question is;
• which information is missing;
• which information is irrelevant;
• where the rule must be verified;
• which alternative interpretations are possible;
• where the risk lies;
• how confident the conclusion can reasonably be.

Experience must also be varied

When selecting a professional adviser, the question “How many years have you worked?” is useful. A better question is: “What kinds of cases have you worked on during those years?”

Why accounting is a particularly difficult domain in which to build expertise

Some professions have fast feedback loops. A chess player makes a bad move and may lose a piece within minutes. A tennis player executes a poor shot and the ball immediately goes out.

In accounting, feedback may arrive after a month, a year, a tax audit, litigation – or never.

Professional experience has an expiry problem

In dynamic fields, accumulated knowledge becomes outdated – particularly in tax law, VAT, international taxation, employment law, social security, financial reporting, digital platforms and e-commerce.

An accountant may have accumulated 30,000 hours of practice. But if some of the internal models being applied were built on legislation from ten years ago, experience itself can begin producing errors.

Sometimes the hardest professional skill is not learning a new rule. It is stopping yourself from automatically applying the old one.

Nine women cannot produce one baby in one month

It is a humorous line, but it contains a serious principle: not every process can be parallelized or accelerated simply by adding more resources.

We can give a young accountant nine mentors. We can give them every professional database, AI, books, courses and dozens of training cases. That may accelerate learning significantly.

But we cannot retroactively give that person ten years of encounters with unexpected situations. We cannot fully compress thousands of real decisions, their consequences and the gradual restructuring of professional perception into a single month.

The principle applies to the surgeon, the craftsperson and the accountant. In some processes, time is not an administrative obstacle. It is part of the production process itself.

How do you work with someone who has already become an expert?

Organizations often make a paradoxical mistake. They invest years in creating an exceptionally capable specialist – and then manage that person as though they were still a novice who needs instructions for every next step.

A highly expert person is not simply an ordinary employee who knows more facts. The expert has developed sophisticated internal models, personal quality-control mechanisms and the ability to recognize problems that the manager may not yet see.

1. Give the expert an objective and boundaries – not a script for every step

For a novice, detailed instructions reduce risk. For an expert, excessive instruction may become interference. In the learning literature, this is related to the expertise reversal effect: guidance that helps people with low prior knowledge can become redundant or cognitively burdensome for highly knowledgeable learners.

2. Autonomy does not mean absence of control

Research on autonomy-supportive leadership links this style with stronger autonomous motivation, satisfaction of basic psychological needs, well-being and positive workplace behavior.

But autonomy does not mean “do whatever you want.” The mature model is:

3. Do not micromanage a process the expert understands better than you do

A manager has every right to determine priorities, deadlines, resources and acceptable risk. But if the specialist was hired precisely because of superior domain knowledge, constant interference with the method can destroy the very reason that specialist was hired.

4. Ask for an explanation of the decision, not ritual obedience

Experts should not become untouchable. Quite the opposite. Strong expertise should be translatable into arguments, assumptions, evidence and clearly stated limits of confidence.

In a complex tax matter, for example, the right control conversation is not “Do it the way we did it last year,” but:

• What are the critical facts?
• Which rule drives the result?
• Where is the interpretive risk?
• What fact could change the conclusion?
• What evidence should we preserve?

5. Protect the expert from work the system can do

The most expensive resource in a highly qualified specialist is not eight hours of attendance. It is a limited supply of high-quality attention.

Routine work should, where possible, be automated, standardized or delegated. Expert attention should be reserved for what is unusual, risky and ambiguous.

6. Give experts access to other strong experts

Expertise can become fragile when a person has nobody capable of challenging their conclusions professionally. One of the most valuable environments for a strong specialist is one where other people can disagree intelligently and with evidence.

This is particularly important in domains with imperfect feedback loops, such as accounting, tax, law and medicine.

7. Do not confuse confidence with expertise

A genuine expert must be able to say “I don’t know,” “I need to verify that,” and “This depends on a fact we do not yet have.” Refusing to give an immediate categorical answer can sometimes be a sign of better judgment, not weaker competence.

8. Do not automatically turn the best specialist into a manager

The ability to solve difficult tax, medical or technical problems is not the same ability as managing people. Promotion “upwards” should not be the only route to higher status and compensation.

9. Give experts time to think

High-quality expert work can look externally as though “nothing is happening”: reading, comparing, checking and thinking. Yet much of the value is being created precisely there.

If every free minute is filled with meetings, status calls, chat messages and administration, an organization may formally use 100% of the expert’s time while practically destroying the most valuable part of the expert’s capacity.

10. Protect expertise from overconfidence

Autonomy must not become a personality cult. Experts also have cognitive biases, can become professionally outdated, and can fall into the trap of “I have done this a hundred times.”

A strong environment combines:

What happens when information is no longer scarce?

AI changes another part of the equation. For a long time, the value of an expert was partly associated with how much information that person could remember. Today, a machine can process in seconds a volume of text that a human could not read in a week.

This does not make expertise unnecessary. It shifts the center of expertise.

An accounting problem is rarely just a mathematical error. It may be a problem of classification, economic substance, contractual relationships, timing of recognition, tax treatment, intent or evidence.

So how do you build a great accountant?

1. Accumulate hours. Without sufficient exposure to real problems, rich mental representations cannot develop.
2. But do not count hours as though they were all equal. One thousand hours of mechanical repetition are not the same as one thousand hours of development.
3. Seek difficult cases. They contain the greatest potential for new learning.
4. Study your mistakes. An analyzed error can become a professional asset. A forgotten one is likely to return.
5. Build feedback systems. Without feedback, we can become extremely experienced at repeating our own mistakes.
6. Learn principles, not only answers. Memorizing an answer solves one case. Understanding the reason solves a family of future cases.
7. Encounter different situations. Variety builds a richer internal library of patterns.
8. Keep knowledge current. In regulated professions, expertise is not a qualification acquired once. It is an ongoing process.

A better rule than the 10,000-hour rule

Hours are the container in which this can happen. They are not the content.

A person does not become a master because time has passed. A person becomes a master because their way of thinking has changed during that time.

10,000 hours of accounting

After roughly a decade of professional practice, an accountant may have seen hundreds of closings, thousands of tax filings, tens of thousands of documents, unusual transactions, errors, audits, discrepancies, legislative changes and – inevitably – some of their own wrong decisions.

But quantity does not automatically create expertise. The difference lies in what the person has done with that experience: merely lived through it, or transformed it into knowledge.

Mastery is the ability to see

At first, the accountant sees an invoice. Later, an accounting entry. Then a tax event. Then a contractual relationship. Then a cash flow. Then the risk.

The truly strong professional gradually learns to see all of those things at the same time.