PipelineRat has put his finger on the thing and I want to expand it, because the indexation framing changes what you should measure and almost nobody measures it.
What tier 2 is actually doing, mechanically
There are three separate effects people bundle together under 'tier 2' and they have completely different evidence behind them.
- Equity amplification. The 2012 model. Junk links raise the tier 1 page's authority, the tier 1 page passes more to you. I think this is dead and I have not seen it work in a controlled test since 2017. I have not tested it at scale since 2019, so treat that as an opinion with an expiry date on it.
- Crawl induction. A link from anywhere gives the crawler a path to the tier 1 page. This is not controversial and it is not really an SEO tactic, it is how crawling works.
- Indexation of the tier 1 page. This is the one that matters commercially, and it is downstream of 2 but not the same thing. Being crawled is necessary and not sufficient.
The measurement most people skip
Before deciding whether tier 2 is worth anything, take your tier 1 link list and check three things for each target page:
- Is the page indexed at all
- If it is, when was it last crawled
- Does your link survive on the live page, and does it survive in the cached copy
I ran this for a client in June across 61 bought links placed over two years. 38 indexed, 14 indexed but not crawled in over four months, 6 never indexed, 3 where the link had been quietly removed after payment. So a shade under two thirds were doing anything at all, and the client had been paying for tier 2 against the whole list without distinguishing.
What I would actually do with the £180
Split it. Spend the first month's budget on the audit above - it is one afternoon with a scraper if you have one, or about that in a spreadsheet if you don't. Then point whatever tier 2 you keep buying only at the tier 1 pages that came back unindexed or stale. Not at all forty. That turns a blanket monthly spend into a targeted one and it makes the effect measurable, because you have a control group sitting right there in your own list.
If after eight weeks the stale ones haven't moved, you have your answer for this client and you cancel with a reason instead of a feeling.
The part I am not sure about
I do not know whether the crawl induction effect persists or whether it is a one-off. My instinct is that a burst of junk links gets you one crawl and then the page reverts to whatever its natural crawl budget was, which would mean tier 2 as a monthly recurring spend is wrong even if tier 2 as a one-off intervention is right. I have never designed a test that separates those cleanly and I would be interested if anyone has.
Summary: stop buying tier 2 for authority, consider buying it for indexation, and only after you have measured which of your tier 1 links are actually indexed.