There is no single official "70/30 rule" in hiring. Several distinct heuristics circulate under the name, and they give quite different advice. Here is each one, and an honest assessment of whether it is worth following.
Version 1: Apply when you meet about 70% of the requirements
The claim: do not wait until you match every bullet point; apply at roughly 70% match.
Verdict: genuinely useful. Job descriptions are wish lists, frequently assembled from several people's preferences, and employers routinely hire candidates who do not meet every criterion. There is well-documented evidence that some groups - women in particular - are more likely to self-select out of applications where they do not meet every listed requirement, which costs them opportunities.
The caveat: which 30% you are missing matters enormously. Missing a mandatory qualification, licence or legal requirement is fatal; missing "experience with a specific software tool" usually is not. Distinguish the hard gates from the preferences.
Version 2: 70% internal, 30% external hiring
The claim: healthy organisations fill roughly 70% of vacancies internally and 30% externally.
Verdict: a reasonable planning heuristic for employers, not a real rule. The right balance varies by growth rate and sector. For a job seeker, though, this version carries a genuinely useful implication: a large share of vacancies are filled internally, which explains why so many advertised roles seem to evaporate, and why getting into an organisation - even sideways - is often easier than getting the specific role you want.
Version 3: 70% of the interview should be the candidate talking
Verdict: sensible guidance, invented number. The underlying principle is sound - an interviewer who talks most of the time learns nothing. As a candidate, aim to answer substantively without monologuing; two minutes per answer with a concrete example is a good target.
Version 4: 70% skills, 30% culture fit in the decision
Verdict: treat with caution. The intent is reasonable, but "culture fit" is where unstructured judgement and bias enter hiring most easily. The evidence favours structured assessment of specific requirements; a vague 30% allocated to fit is frequently where consistency breaks down. Employers are better served by defining the behaviours they actually mean and assessing them consistently - see statistics in hiring decisions.
The general point about numbered rules
Business folklore is full of precise-sounding ratios with no evidential basis. Some encode real wisdom in a memorable form; others are numbers someone invented that then spread because they sound authoritative. The test is always: what evidence supports this figure, and what would change it in my situation?
That is a statistical habit rather than a hiring one - and it applies equally to the rule of 3 and every other numbered rule you will encounter.
The one to actually use
Version 1, with the caveat about hard gates. If you meet most of the substantive requirements and none of the mandatory ones are missing, apply.
Developing the instinct to interrogate quoted figures is what the Statistics for Business course at London School of Business UK is really about. Enquire today.