CSS switch in client reports: the metrics that prove it

The CSS advantage works in the auction, where nobody can watch it directly. Your client sees it only through the figures in Google Ads, and those figures move for many reasons at once.

A good report separates the CSS effect from the noise: a fixed starting point, the right metrics, fair comparison periods and an honest explanation when the CPC doesn't do what everyone expected.

Fix the starting point before the switch

The most common mistake happens before the switch: nobody records how things stood. Afterwards, every comparison is an argument.

Note the switch date in your report and change log, so every later chart can be read against it.
Export the baseline: cost, average CPC, clicks, impressions, impression share, conversions, conversion value and ROAS of the Shopping campaigns for the four to eight weeks before the switch.
List other planned changes such as new bidding targets, budget changes or a feed overhaul. If possible, keep them out of the first weeks after the switch.

Because the Google Ads account does not need to be switched, all historical data stays in the same account and remains directly comparable. Source: Google Merchant Center Help

The metrics that show the effect

No single metric tells the whole story. Read them together:

Metric	What it shows	What to look for
Average CPC	The price per click	Falls if bids stay at the same level
Clicks	Reach	Rises if the budget stays the same
Impression share	How often the ads appear in eligible auctions	Rises if the stronger bid wins more auctions
Conversions and conversion value	The result	Follow the clicks if the conversion rate holds
ROAS and cost per conversion	Efficiency	The figure your client cares about most

Report on the Shopping campaigns separately. In Performance Max, the CSS advantage concerns Shopping inventory only, so a blended figure across Search, YouTube and Display dilutes the effect.

An example report

This is how a one-month comparison can look when the budget stays the same and the average CPC falls by a fifth:

Example: Shopping campaigns, one month before and after

Before the switchAfter the switch

Ad cost

£10,000

Average CPC

£1.00

£0.80

Clicks

10,000

12,500

Conversions

200

250

Conversion value

£50,000

£62,500

ROAS

500%

625%

Cost per conversion

£50.00

£40.00

Illustrative example, not a forecast. Same budget, CPC 20% lower, conversion rate and order value held constant.

The example keeps the conversion rate (2%) and the average order value (£250) constant, so the extra clicks turn into extra conversions one to one. In a real account both move, which is why the report shows all rows and not just the last one.

Why the CPC doesn't always fall

Sometimes a client sees the average CPC stay where it was and concludes that the switch did nothing. Usually the advantage just took a different form.

Automated bidding strategies such as target ROAS or maximise conversion value use the stronger bid to win more auctions instead of paying less per click. The CPC then stays level while impression share, clicks and conversion value rise.

On top of that come effects that have nothing to do with the CSS: seasonal demand, new competitors, price changes in the feed or products going out of stock. They can hide the advantage in the CPC or exaggerate it.

The CSS advantage shows up either as a lower price per click or as more volume at the same price. Read CPC, impression share and ROAS together, never the CPC alone.

Choose comparison periods that hold up

Same length, same weekdays. Compare four weeks with four weeks, not a month of 31 days with one of 28.
Mind the season. November against October measures Black Friday, not the CSS. If the account has history, compare the same weeks of the previous year as well.
Leave out the switch days. The days in which the change takes effect belong to neither period.
Keep other changes visible. If budgets or bidding targets changed in between, say so in the report instead of crediting everything to the CSS.

Make your agency's name part of the result

With White Label CSS, your agency's CSS name appears under your client's Shopping ads. That is the one part of the effect your client can see with their own eyes, so put it in the report.

A screenshot of one of the client's Shopping ads showing your name next to the before-and-after figures connects the result to your work. It also makes clear that the advantage comes from your agency, not from a tool somewhere in the background.

A report rhythm your client understands

After four to six weeks: a first one-page comparison with cost, conversion value and ROAS before and after, plus one sentence on what they mean.
Every month: the same figures continued, so the trend becomes visible instead of a single snapshot.
Every quarter: a comparison with the same quarter of the previous year, which takes most of the seasonal noise out.

Keep the format the same every time. When a client can read the report in two minutes, the CSS stops being a one-off project and becomes a fixed part of what your agency delivers.