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Net effective rent is the figure most likely to disagree between two comp providers looking at the same lease. The rent might read $45.00/SF on the lease document, but the number that lands in a comp database depends on how that provider defines rent and treats concessions, and when it captured the deal. Pull the same deal from two sources and you can get two defensible answers that simply aren’t the same number.
That gap matters more than it should. Underwriting and appraisal review depend on comp data holding up under scrutiny. So does portfolio benchmarking. If the inputs don’t match, neither will the outputs.
Key Takeaway: Net effective rent differences between comp databases are rarely errors. They’re usually the product of different definitions (starting vs. net effective vs. adjusted effective rent), different concession treatment, different capture timing, and different verification standards. Understanding which convention a database uses matters as much as the number itself.
What Is Net Effective Rent?
Net effective rent is the average monthly rental cost of a lease after subtracting the value of concessions from the stated rent over the term. It answers a specific question: what is the tenant actually paying, once free rent and improvement allowances are accounted for, rather than what the lease document lists on its face.
That’s distinct from a few adjacent terms that get used interchangeably, and shouldn’t be:
- Starting Rent is the rent/SF at lease commencement, before any concession math.
- Net Effective Rent nets free rent and Work Value against the term to produce an average monthly cost.
- Adjusted Effective Rent grosses up that figure to an annualized number that fully incorporates TI allowances and free rent, which is useful for comparing deals with very different concession structures side by side.
- Current/In-Place Rent is whatever rent is being paid as of the date the data was pulled, which may be well past lease commencement and reflect escalations already in effect.
A comp record that reports “starting rent” and one that reports “net effective rent” for the same lease will not match, and that’s by design, not an error. The first problem in reconciling two databases is confirming they’re even answering the same question.
Why Two Comp Databases Can Show Different Numbers for the Same Deal
The short answer: methodology, not fraud. Four factors drive most of the variance.
Concession treatment. Free rent and Work Value (CompStak’s field name for TI allowance) both lower the effective cost of occupancy. A database that estimates concessions instead of sourcing them from the lease abstract, or that omits Work Value entirely, will land on a different net effective rent than one built from verified concession terms.
Calculation convention. Straight-lining free rent evenly across the term produces a different monthly figure than front-loading it. Databases that don’t disclose their convention leave analysts guessing which method underlies the number they’re comparing.
Timing of capture. A comp logged at lease signing looks different from one updated after a renewal, expansion, or blend-and-extend. If one provider refreshes records and another doesn’t, the same address can carry two different rent histories.
Source and verification standard. Broker-reported figures and public record filings don’t carry the same reliability as analyst-reviewed submissions checked against the source document. A number pulled from an unverified third-party source and never reconciled against the actual lease will drift from a number that was.
How Concession Treatment Skews Net Effective Rent Calculations
Concessions are the single biggest swing factor in net effective rent, and they’re also the easiest place for two databases to diverge. Free rent, expressed as a share of term, and Work Value per square foot together make up the concession package. A longer free rent period or a richer TI allowance can pull net effective rent well below the headline starting rent, even when the lease document shows a market-looking asking number.
This is precisely why concession ratio (free rent plus Work Value/TI per SF) shows up as a standalone metric in CompStak’s data rather than getting buried inside a single blended rent figure. Separating the components lets an analyst see whether a rent move is coming from base rent or from the concession package, and it lets two databases be compared component by component instead of as one opaque total.
What Makes a Comp Database Accurate?
Accuracy in a comp database comes down to independent verification, not just volume. A high comp count means little if a meaningful share of those records were never checked against a source document. Every comp CompStak receives is processed by a multi-step data verification system, including machine learning algorithms, statistical anomaly detection, and a team of CRE data analysts, before it enters the dataset.
That process matters most at the entity level. The same tenant can appear under a parent company name in one record and a subsidiary name in another, and the same building can be listed under different addresses across sources. CompStak resolves those inconsistencies through its CRE ontology, so a tenant’s full leasing history rolls up correctly instead of fragmenting across records that look unrelated but describe the same company.
Comps shared through CompStak Exchange follow this same review path before they’re published. That’s the structural difference between a crowdsourced database and an analyst-reviewed one: crowdsourcing supplies the volume, and verification determines whether that volume is usable.
Data from CompStak’s proprietary database. Learn more at compstak.com.
How the Columbia CompStak Rent Index Solves the Comparability Problem
The Columbia CompStak Rent Index (CCRI), developed with Columbia Business School, addresses a comparability problem that sits above the individual comp: two averages of net effective rent can move differently even when both are accurate, simply because the mix of deals that closed in a given quarter shifted. A period with a cluster of large Prime Class A leases will pull a simple average up, independent of whether market rents actually moved. The CCRI is quality-adjusted specifically to control for that compositional noise, so its trendline reflects underlying rent movement rather than which deals happened to close.
As of May 2026, the national Columbia CompStak Rent Index stood at $36.39/SF for office (+7.4% YoY), $33.74/SF for retail (+1.5% YoY), and $11.92/SF for industrial (+3.9% YoY). Those figures can diverge from a raw average of net effective rents pulled from the same underlying comps, and that divergence is the point: it isolates rent growth from the noise of deal mix.
For an analyst reconciling two comp sources, that has a practical implication: if one provider’s average net effective rent is moving sharply from quarter to quarter while a quality-adjusted index for the same market is flat, the swing is more likely coming from which deals closed than from an actual shift in market rent.
Source: Columbia CompStak Rent Index (CCRI), developed with Columbia Business School. Data as of May 2026.
FAQ
What is net effective rent in a lease comp?
Net effective rent is the average monthly rental cost of a lease once free rent and Work Value (TI allowance) are netted against the stated rent over the term. It reflects what a tenant actually pays, not the headline rent listed on the lease.
Why do two comp databases show different numbers for the same deal?
Most often because they define rent differently, such as starting rent versus net effective rent versus adjusted effective rent, or because they handle concessions, timing, and verification differently. Rarely is either number simply wrong; they’re usually answering different questions.
How does concession treatment affect net effective rent?
Free rent and Work Value both lower effective rent below the stated rate. A database that estimates or omits concessions will produce a different net effective rent than one sourced directly from the lease.
What’s the difference between net effective rent and adjusted effective rent?
Net effective rent nets concessions against the term to produce an average monthly cost. Adjusted effective rent grosses that figure up into an annualized number, which is useful when comparing deals with very different concession packages.
How does CompStak verify comp database accuracy?
Every comp goes through a multi-step verification system, including machine learning algorithms, statistical anomaly detection, and analyst review, before it’s added to the dataset.
What is the Columbia CompStak Rent Index (CCRI)?
The CCRI is a quality-adjusted net effective rent index co-developed with Columbia Business School. It controls for shifts in the mix of leased space over time, isolating actual rent movement from changes in which deals closed in a given period.
Why does the CCRI move differently than a simple average of net effective rents?
A simple average is sensitive to deal mix: a quarter heavy with large Prime Class A leases will pull the average up regardless of market rent movement. The CCRI adjusts for that compositional effect.
Can lenders and appraisers rely on crowdsourced comp data?
Yes, when that data is independently verified before use. Comps shared through CompStak Exchange are analyst-reviewed and entity-resolved before publication, which separates verified crowdsourced data from unreviewed broker submissions.
