Online Advertising
The tighter the audience the better the advertising. That held until about 2021 and is now the most expensive misconception in most accounts.
Anyone advertising on Facebook in 2018 learned to cut audiences as narrowly as possible: job, interests, life events, all combined. That technique no longer works, and the reason is not privacy but arithmetic.
Delivery runs through an auction per ad slot. The smaller the pool of possible recipients, the more often the same person must be addressed to spend the budget. Rising frequency means falling response and rising cost.
| Audience size | Typical weekly frequency | Effect |
|---|---|---|
| under 50,000 | 6 to 12 | fatigue after 10 days |
| 100,000 to 500,000 | 3 to 5 | tolerable for short bursts |
| 500,000 to 2 m | 1.5 to 3 | the norm for continuous running |
| over 5 m | under 1.5 | only sensible with a strong creative |
Not all audience types are worth the same. This order holds up in practice.
An ad set leaves the learning phase at roughly 50 conversions in seven days. Below that it stays permanently in learning and results swing hard.
Do that sum before you build. At £40 per enquiry you need £2,000 a week per ad set to clear the bar. If your total budget is £1,200 a month, you may run exactly one ad set, not five.
When two ad sets reach the same people you bid against yourself. The system tries to prevent it and does not fully succeed.
Practical rules: always exclude the remarketing audience from the prospecting set; exclude existing customers from acquisition campaigns except for repeat purchases; never run lookalikes of different percentage tiers in parallel, only the larger; and keep to at most three ad sets per campaign, or overlap is unavoidable.
Uploading a customer list is a processing of personal data. You need a legal basis, normally a consent that names this purpose explicitly. A newsletter consent does not automatically cover advertising delivery on a platform.
Likewise the measurement tool on your site needs consent before it loads. Get either wrong and you risk not only a fine but the loss of the whole data base if challenged.
For budgets between £500 and £3,000 a month this lean build has proven itself: one campaign, conversion objective, budget at campaign level; ad set A broad, location and age only, no interests; ad set B remarketing of the last 30 days, excluded from A; three to four creatives per ad set, at least one of them vertical.
Anything beyond that is fine-tuning that only pays above roughly £5,000 a month.
For a national market, 500,000 to 2 million people is a good starting range. Below 100,000 the cost per thousand climbs sharply because the same people are hit too often.
Less and less. They now act as a starting signal for the algorithm rather than a hard boundary. As sole steering they no longer work.
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