Compare periods — performance over time
The Compare to previous period toggle in the Analytics date picker adds a per-metric delta to the KPI grid. Common pairs: last 7d vs prior 7d, MoM, YoY.
Written By Salvatore Sinigaglia
Last updated About 1 hour ago
The Compare to previous period toggle in the Analytics date picker adds a per-metric delta to the KPI grid. Common pairs: last 7d vs prior 7d, MoM, YoY.
Compare periods — performance over time
In Wevion Analytics, the Compare to previous period toggle in the date picker turns on period-over-period comparison. Each KPI card then shows its current value plus a delta versus the previous period, coloured by whether the change is an improvement for that metric. By default the previous period is auto-derived (last 7 days → the prior 7 days); you can also set a custom comparison range for cases like year-over-year. Standard pairs: last_7d vs prior_7d, MoM (month-over-month), YoY (year-over-year).
Who is this for
Anyone reading "is this getting better or worse?" — the most common analytics question after "what's the number now?".
How comparison works
Comparison uses two date ranges:
For each metric, the KPI grid then shows the current value and the change (delta) versus the previous value.
UI options
Toggle "Compare to previous period"
A toggle inside the date picker. By default it auto-derives the previous range from the current one:
- Last 7 days → previous 7 days
- Last 30 days → previous 30 days
- Custom range → previous range of the same length
Quick and automatic.
Pick a custom previous range
For non-standard comparison (e.g. last 7 days vs the same week last year):
- Open the date picker
- Set the current range
- Enable compare and choose the custom comparison type → set the previous range
- Apply
Useful for YoY when calendar weeks differ.
Standard comparison pairs
How the delta is rendered
Each card in the KPI grid shows:
- Current value (large)
- The delta versus the previous period (small, coloured)
Colour direction depends on the metric:
(Same as KPI strip color conventions per an-106.)
Period length matters
Match period length to comparison intent:
For ROAS comparisons: 7 days minimum (postback lag).For pace comparisons (CTR, spend): 1-3 days OK.For executive monthly: 30 days.
Caveats
Postback lag affects "current" period
If current_until is today: postback metrics (purchases, ROAS, CPA) are incomplete. Delta_pct may swing significantly in the next 24-72h as data settles.
For decision-grade comparisons: end the current range 2-3 days ago.
Seasonal pairs need YoY
Comparing last 7d (mid-November) to prior 7d misses the Black Friday seasonal effect.
For seasonal businesses: pair with the same period last year (YoY) for a fair comparison.
Currency stability
The display currency applies to both periods. FX-rate variation between periods can introduce minor noise — generally < 1-2% for major currency pairs. See an-115.
Use cases
Monday weekly review
- Set the current range = last_7d
- Enable Compare to previous period (auto = prior 7d)
- Read the deltas on the KPI grid and the per-account table
- Action: shift budget toward improving accounts; investigate declining ones
Monthly executive report
- Set the current range = last_30d
- Compare to previous period (prior 30d)
- Export CSV / Excel with the period's daily rows
- Annotate with commentary
MoM YoY combined
- Show last month's delta vs the prior month
- Then show the same month YoY (vs 12 months ago)
- Captures growth trajectory + seasonality
Pre-meeting prep
Before a stakeholder meeting: set the period, enable Compare, then export CSV / Excel (an-116) and annotate with talking points.
How it relates to Ads Manager comparison
Ads Manager also has its own period comparison (am-120). Differences:
Use both: Analytics for direction, Ads Manager for action.
Common mistakes
- Comparing 7d vs 30d: different period lengths = misleading deltas. Match lengths.
- YoY with calendar mismatch: same dates ≠ same shopping week (e.g. Black Friday shifts). Use ISO-week pairing.
- Reading delta_pct on incomplete current period: postback lag falsifies "current". End 2-3 days ago for ROAS decisions.
- Ignoring base value with high delta_pct: +500% from €10 to €60 is not the same as +500% from €1.000 to €6.000. Read both.
- Color interpretation without metric awareness: down on CPC = good (cheaper); down on ROAS = bad. Check direction per metric.
FAQ
How do I compare two periods in Wevion analytics?
Enable the Compare to previous period toggle in the top toolbar, which auto-derives the previous range from your current one (last 7 days becomes the prior 7 days). For non-standard comparisons, use the date range picker's Custom comparison to set previous_since and previous_until manually, useful for year-over-year when calendar weeks differ.
What does delta_pct mean and how is it colored?
Wevion's comparison returns delta_pct, the percentage change of the current period versus the previous one, shown small and colored next to each metric. The color direction depends on the metric: up is green for spend, conversions, revenue, ROAS, and CTR, while down is green for CPC, CPM, CPA, and frequency because cheaper or lower fatigue is better.
What are the standard comparison pairs?
Wevion supports week-over-week (last_7d vs the prior 7 days), month-over-month (last_30d vs prior_30d), year-over-year (last_30d vs the same period last year for seasonality), and quarter-over-quarter (last_90d vs prior_90d). Match period lengths so deltas stay meaningful.
Why is my delta_pct swinging on the current period?
Because postback metrics like purchases, ROAS, and CPA are incomplete when current_until is today, and delta_pct can shift significantly over the next 24-72 hours as data settles. For decision-grade comparisons, end current_until two or three days ago, and use at least a 7-day period for ROAS.
Should I use Analytics comparison or Ads Manager comparison?
Use both for different jobs. Wevion's Analytics comparison is aggregated and strategic, adding deltas to the KPI grid and per-account table to drive allocation and scale decisions. Ads Manager comparison is row-level and tactical, showing per-entity deltas so you can pause or scale a specific entity. Analytics gives direction; Ads Manager drives the action.