Market segmentation means dividing a heterogeneous market into groups of buyers who share something that predicts how they'll respond to marketing, so each group can be served with a distinct approach rather than one average offer aimed at everyone (Smith, 1956). Smith's 1956 article introduced segmentation as an alternative to pure product differentiation; it took Kotler folding segmentation, targeting and positioning into one taught sequence, beginning with early editions of Marketing Management, for STP to become the three-step discipline taught today (Kotler and Keller, 2016). The point of the exercise is practical, not academic: a market segmented well lets you spend a finite marketing budget on the buyers most likely to respond to it, rather than diluting that budget across everyone.

Four bases are in common use, and each groups buyers by something different. Demographic segmentation groups by age, income, household composition or life stage — cheap to measure and easy to buy media against, but a demographic group doesn't itself explain why people buy. Behavioural segmentation groups by what buyers actually do: usage rate, purchase occasion, brand loyalty, price sensitivity. Psychographic segmentation groups by lifestyle, values and personality — why someone buys, even when demographics look identical. Needs-based, or benefit, segmentation groups buyers by what they want from the category itself, which Haley (1968) proposed as a more decision-useful alternative to grouping people by who they are: two buyers with identical ages and incomes can want completely different things from the same product, and a segmentation built on that difference often predicts their response to an offer better than one built on their age bracket.

None of the four bases is always the right starting point. A convenience-food category might segment best by purchase occasion, a behavioural basis, because that's what actually changes what people buy; a life-insurance category might segment best by life stage, a demographic basis, because that closely tracks real need. A soft-drinks category, Birchwater's own, tends to segment best on a mix of needs and lifestyle, because two buyers of identical age and income can want completely different things from the same drink. The test is empirical, not a rule to apply by habit: whichever basis best predicts how a given group of buyers will actually respond to your offer is the right one for that category, and that has to be checked against evidence, the kind generated in Module 2, rather than assumed.

A segmentation on its own is just a map; the next job is deciding which part of it to serve. Jobber and Ellis-Chadwick (2019) group that decision into four practical criteria: size and growth, is the segment big enough now, and is it growing or shrinking; profitability, will serving this segment generate margin, not just revenue; accessibility, can you actually reach it with the channels and budget you have or can build; and strategic fit, does serving it play to your existing strengths and brand, or pull the organisation somewhere it has no real capability. A segment can fail on any one of these even while it looks attractive on the others — large and growing but unreachable without a distribution network you don't have, or profitable but a poor fit for a brand built on something else entirely.

Profitability is the criterion most often guessed at rather than evidenced, and it's exactly where Module 2 finding earns its keep: health-conscious professionals' over-index on willingness to pay a premium and under-index on price sensitivity isn't a demographic fact, it's direct evidence that this segment scores high on profitability specifically, because willingness to pay converts more directly into margin than almost any other single number a segmentation exercise can produce. Scoring a segment on profitability without a number like this is really just an assumption dressed up as an assessment.

Scoring a candidate segment against each criterion, then weighting the criteria by how much they matter to the decision in front of you, turns four separate judgements into one comparable number per segment — precisely what Segment Attractiveness Scorecard does for a set of candidate segments side by side. Weighting matters because the criteria aren't always equally important: a cash-constrained challenger brand might weight profitability and accessibility above raw size, while a well-funded entrant chasing scale might weight size and growth higher. The output is a ranking, not a verdict handed down by the tool — a low-scoring segment that still matters strategically, for defensive reasons or because it funds something else, is a judgement call the scorecard informs rather than makes for you.

Once segments are ranked, the next decision is how many to serve and how distinctly. Kotler and Keller (2016) set out four targeting strategies along a spectrum of how tailored the approach gets. Undifferentiated, or mass, targeting treats the whole market as one segment and serves it with a single offer — cheap to run but increasingly rare, because almost any market splits into groups that want genuinely different things. Differentiated targeting serves several segments with a distinct offer for each, trading higher cost and complexity for a message that actually fits each group. Concentrated, or niche, targeting puts most resource behind a single segment and accepts the risk of depending on it. Micro-marketing narrows further still, tailoring to local markets or even individual buyers, which digital targeting has made far cheaper than it used to be, but which still demands data and systems most organisations don't have by default.

The strategies trade resource for fit, and that trade-off is the actual decision, not a label applied after the fact. Differentiated targeting usually costs more than concentrated targeting because every extra segment served needs its own message, and sometimes its own product variant or channel; it also spreads a limited budget thinner, which can leave every segment under-served rather than one well-served. Concentrated targeting, in exchange for lower cost and a sharper message, accepts a single point of failure: if that one segment's needs shift, or a well-funded rival moves in on it, there's no second segment's revenue to fall back on. Choosing between them means weighing Lesson 3.2 against how much the organisation can actually afford to run two tailored approaches well, rather than one or several run thinly.

Birchwater's own choice sits between concentrated and differentiated: rather than serving all three candidate segments evenly, it commits most of its resource to health-conscious professionals as the primary target, serves convenience grazers as a secondary target with a lighter version of the same approach, and deliberately doesn't target price-sensitive families at all. That's a resourcing decision as much as a marketing one — spreading evenly across three fundamentally different segments would have diluted the message to all three, where committing to one primary segment backed by a smaller secondary one doesn't.

Positioning is the last step of STP and the one with the most separate parentage: where Smith supplied segmentation in 1956, the concept of positioning itself is usually traced to Jack Trout and Al Ries, whose Advertising Age series argued that a brand wins not by being different in the product but by owning a distinct, defensible place in the buyer's mind relative to named alternatives (Ries and Trout, 1972). A positioning statement states that place concisely: the target segment, the category the offer competes in, and the single most important reason that segment should choose it over the alternatives actually available to them.

The discipline that separates a real positioning statement from a slogan is a stress test: could a named competitor credibly make the same claim? Aaker and Shansby (1982) warn that a position is only differentiated if it's both important to the target segment and genuinely hard for competitors to copy or claim; a claim that sounds distinctive but that any rival in the category could say with equal credibility isn't a point of difference, it's just wording. Testing a positioning statement means naming the real alternative a buyer would otherwise choose and asking, specifically, whether that competitor could say the same thing and be believed.

Birchwater positions itself as "the lower-sugar sparkling water that actually tastes like something" — a statement built on two things it can actually prove: a wider flavour range than most competitors carry, and a lower-sugar recipe than standard soft drinks. Run against the stress test, the claim holds specifically because of who it's tested against. AquaVolt, the mass-distributed, no-sugar flavoured-water line from a major drinks group, competes on scale and price rather than flavour range, so it can't credibly claim the same combination of lower sugar and genuine flavour variety without contradicting the stripped-down, mass-market positioning its own price point depends on. The same claim would fail the stress test against a specialist competitor matching Birchwater's flavour range at a similar price — which is exactly why a positioning statement has to be checked against the real alternative each target segment would otherwise choose, not against competitors in the abstract.