Is 80% of your budget trapped in one campaign?

Start from performance rather than policy: measure each campaign's ROAS, impression share lost to budget, and contribution margin, then allocate so that no campaign is budget-constrained at positive marginal ROI and no campaign is over-funded beyond the point where marginal ROAS drops below target. For most multi-campaign accounts, the right structure is roughly 60% Search (split brand/non-brand), 25% Shopping or PMax, 15% YouTube/Display — but this is a starting framework, not a rule. Starved winner campaigns (high ROAS, budget-capped) should receive budget increases before poorly-performing campaigns get cuts. The Spend Concentration Audit calculates your current allocation, flags starved winners and over-funded losers, and produces a rebalance matrix with SCALE / HOLD / CUT tags per campaign.

You are running a shared daily budget where Google's auction logic has concentrated spend on whichever campaign it scores as highest-converting — typically a brand campaign or a PMax campaign. Split the shared budget into per-campaign daily budgets sized to each campaign's performance, remove any portfolio bid strategies that are amplifying the concentration, and consider moving the dominant campaign to its own standalone budget so its pacing doesn't starve others. This rebalance takes effect within 7–14 days. The Spend Concentration Audit surfaces every shared-budget allocation imbalance and produces the per-campaign budget split that restores healthy distribution.

For each campaign, check Impression Share Lost to Budget — if above 15%, the campaign is budget-constrained and could spend more profitably. Size daily budget at 20–30% above the amount required to eliminate budget-based impression share loss (not exactly at it, because daily spend fluctuates). For multi-campaign accounts, total your per-campaign requirements and compare to your overall budget envelope — if the total exceeds your envelope, cut from campaigns with below-target ROAS first, not from starved winners. The Spend Concentration Audit ranks all campaigns by Impression Share Lost to Budget and produces the specific budget increment each starved winner needs.

Look for the 'Limited by budget' status tag in the Campaigns view and check two metrics per campaign: Search Impression Share Lost (Budget) and Daily Spend vs Daily Budget ratio. A campaign hitting 95%+ of daily budget consistently and reporting 15%+ impression share lost to budget is constrained. A campaign hitting 95%+ of budget without impression share loss is just pacing normally. Budget-constrained campaigns with above-target ROAS are your priority scaling candidates. The Spend Concentration Audit identifies all budget-constrained campaigns, quantifies the specific conversion volume each is missing, and estimates the revenue unlock from removing the budget cap.

There is no universally correct split — it depends on your business model (ecommerce skews Shopping/PMax, lead-gen skews Search), account maturity (younger accounts with less conversion data should skew Search for controllability), and margin structure. A starting framework for ecommerce: 40% Search, 35% Shopping/PMax, 15% YouTube/Display, 10% brand defence. For lead-gen: 70% Search, 15% PMax, 10% Display remarketing, 5% YouTube. Revisit every 90 days as performance data accumulates. The Spend Concentration Audit produces your current split, benchmarks it against category norms, and recommends the rebalance direction based on per-channel ROAS performance.

Rebalance in 30–50% increments, not all at once — move 30% of a losing campaign's budget to a winning campaign, wait 5–7 days for Smart Bidding to adapt, then assess before moving more. Avoid redirecting budget to campaigns already in learning phase (adds volatility), and hold the losing campaign's reduced budget stable for at least 14 days before cutting further (some low-performance periods are seasonal, not structural). Never rebalance more than 20% of total account budget in a single day — the algorithm panics. The Spend Concentration Audit produces a rebalance matrix with exact amounts and timing recommendations.

In terms of spend distribution alone: 15–25% brand, 75–85% non-brand is the healthy range for most accounts — reflecting that brand should capture existing demand efficiently while non-brand funds growth. Accounts with brand spend above 40% are usually over-defending and under-acquiring. Below 10% typically means you are unprotected against competitor bidding on your brand. The Spend Concentration Audit reports your current split, cross-references against brand dependency ratio (brand conversions as a share of total), and recommends whether to shift budget.

Three levers: (1) set campaign-specific daily budgets rather than shared budgets when campaigns have different ROAS profiles, (2) split a dominant campaign into smaller campaigns when one grows past 40% of total account spend (large campaigns capture disproportionate auction priority), (3) avoid portfolio bid strategies across mixed-performance campaigns — they amplify concentration by prioritising whichever campaign hits the target first. The Spend Concentration Audit flags every over-funded campaign and recommends specific structural changes rather than just budget cuts.

Portfolio bid strategies work well for campaigns with similar target ROAS or target CPA values and similar conversion volume — they let Smart Bidding rebalance bids across grouped campaigns automatically. They work badly when you combine campaigns with materially different margins, conversion volumes, or business goals — the algorithm over-prioritises whichever campaign produces easy wins and starves the others. Only group campaigns that share business purpose (e.g., all non-brand Search campaigns for a single product line). The Spend Concentration Audit checks your portfolio strategy groupings and flags incompatible groupings that are causing concentration.

A starved winner is a campaign with strong ROAS and strong conversion rate being held back by an insufficient daily budget — it exhausts its allocation before the day ends, missing auctions during your highest-converting hours. You identify them by the combination of high Impression Share Lost to Budget (15%+) and above-average ROAS. They are the opposite of the concentration problem — instead of over-funding a weak campaign, you are under-funding a strong one. The Spend Concentration Audit ranks all starved winners by estimated daily revenue left on the table, so you know which to unlock first.

No single campaign should absorb more than 50% of total account budget unless it consistently outperforms your target ROAS by at least 1.5x and has confirmed impression share headroom to scale into. Even then, maintaining at least 2–3 additional active campaigns provides resilience — if the dominant campaign enters a learning phase, faces a Quality Score change, or hits new competition, your account does not collapse. Concentration above 70% in a single campaign is fragile enough to be a business risk, not just a PPC issue. The Spend Concentration Audit calculates your Budget Gini Index (a measure of concentration across campaigns) and flags when your top-campaign share exceeds safe thresholds for your spend level.