Anticipated Expansion of Purchases Scale (AEP)

Abstract

The Anticipated Expansion of Purchases Scale (AEP) is a psychometric and organizational measurement instrument developed by Joseph P. Cannon and Christian Homburg (2001) to assess an industrial customer organization’s strategic intention to increase its future transactional volume and market share of wallet with a designated focal supplier. Introduced within the seminal empirical investigation titled Buyer–Supplier Relationships and Customer Firm Costs published in the Journal of Marketing, the scale serves as a core relational performance outcome capturing the forward-looking economic value derived from close interorganizational collaboration. In industrial supply networks and business-to-business (B2B) relationship marketing, customer retention and expansion represent pivotal drivers of sustainable supplier profitability. The AEP conceptualizes purchase expansion not as an immediate transactional decision, but as a deliberate, forward-looking operational commitment spanning medium- and long-term planning horizons.

Methodologically, the AEP operationalizes buyer expansion intentions via a concise, multi-item psychometric structure evaluated on seven-point Likert scales ranging from strong disagreement to strong agreement. The measure captures two primary dimensions of purchase intent: quantitative growth in overall purchase volume and relative growth in the proportion or share of business allocated to the supplier vis-à-vis alternative market sources. Extensive empirical testing across diverse manufacturing sectors has demonstrated robust psychometric properties, including high internal consistency reliability (composite reliability exceeding .85; Cronbach’s alpha values typically ranging between .84 and .89) and strong convergent, discriminant, and criterion-related predictive validity. By bridging organizational psychology, microeconomics, and supply chain management, the AEP provides researchers and procurement strategists with a reliable, statistically validated tool to assess the relational yield of supplier investments, structural integration, and relational governance mechanisms.

Keywords

Anticipated Expansion of Purchases, AEP Scale, Buyer-Supplier Relationships, Relationship Marketing, Customer Share of Wallet, Interorganizational Governance, Relational Performance, B2B Procurement, Industrial Purchasing, Customer Retention, Transaction Cost Economics, Psychometrics

Authors

The Anticipated Expansion of Purchases Scale was conceptualized, operationalized, and statistically validated by two prominent scholars in the domain of interorganizational relationship marketing and strategic management:

• Joseph P. Cannon, Ph.D.: Professor of Marketing at the College of Business, Colorado State University, Fort Collins, Colorado, USA. Dr. Cannon is an internationally acclaimed researcher whose scholarship focuses on business-to-business relationships, buyer-seller collaboration, strategic sourcing, and distribution channels. His work has been widely published in flagship marketing journals, including the Journal of Marketing, Journal of Marketing Research, and Academy of Management Journal.
• Christian Homburg, Dr. rer. pol. Dr. h.c. mult.: Professor of Marketing and Chair of the Marketing Department at the University of Mannheim, Germany, and Professorial Research Fellow at the Alliance Manchester Business School, University of Manchester, UK. Professor Homburg is recognized among the most prolific and influential marketing scholars globally, specializing in market-oriented management, customer relationship management (CRM), sales management, and industrial business-to-business marketing strategy.

Purpose

In business-to-business contexts, transactional volume and customer lifetime value dictate supplier viability. Traditional accounting metrics are fundamentally retrospective (lagging indicators), reflecting historical purchases rather than ongoing relational health. The Anticipated Expansion of Purchases Scale was designed to fill a critical methodological void by delivering a reliable, forward-looking (leading) indicator of customer behavioral intent. Specifically, the scale evaluates the degree to which a buying organization plans to expand its operational dependency on a vendor by allocating higher absolute dollar volumes and a larger proportion of its total category purchasing requirements to that supplier over subsequent operating cycles.

From an applied organizational research perspective, the AEP scale allows scholars and management consultants to isolate the exact mechanisms through which supplier relationship management (SRM) practices translate into tangible commercial rewards. Suppliers routinely invest heavily in relationship-specific assets, enterprise software integration, dedicated account teams, and co-development initiatives. Measuring actual historical sales changes often introduces substantial empirical noise due to macroeconomic volatility, raw material supply shocks, or corporate mergers. In contrast, the AEP captures cognitive and strategic commitments formulated by organizational purchasing decision-makers, isolating the true relational yield of collaborative investments.

Furthermore, within empirical organizational psychology, the scale provides insight into institutional decision-making under uncertainty. Industrial purchasing decisions rarely involve an isolated individual; rather, they reflect the collective judgment of a Buying Center comprising procurement officers, technical engineers, finance executives, and operations managers. The AEP synthesizes these cross-functional considerations into a standardized psychometric index, capturing the customer’s perceived reduction in supplier-related risk and the concurrent anticipation of superior total cost efficiency. Consequently, the scale has broad applicability across supply chain risk audits, vendor satisfaction benchmarking, customer equity modeling, and cross-sectional studies on inter-firm governance.

Psychological Construct

The psychological and behavioral construct tapped by the AEP is rooted in organizational behavioral intention, defined within industrial psychology as a formalized strategic inclination to engage in cooperative, mutually reinforcing transactions with a partner firm. In contrast to individual consumer purchasing intentions, which may stem from spontaneous affective or impulsive impulses, organizational anticipated expansion reflects a systematic, calculative, and norm-governed alignment between two corporate entities. The construct comprises two core underlying facets:

1. Absolute Purchase Volume Expansion

This facet assesses the buying organization’s intention to increase the aggregate physical or monetary volume of goods and services procured from the focal supplier. This expansion reflects growing organizational trust, technological compatibility, and operational alignment. When an industrial buyer anticipates purchasing a higher quantity of components, subassemblies, or service packages from a single supplier, it signals that the supplier’s quality control, pricing structure, and delivery reliability have successfully reduced the buyer’s internal operational and procurement costs.

2. Relative Share of Wallet (Category Allocation)

The second essential facet focuses on relative allocation, commonly conceptualized as share of wallet. Most industrial enterprises adopt dual-sourcing or multi-sourcing strategies to mitigate supply disruption hazards and maintain competitive price pressure across vendors. Consequently, a buying firm may increase its absolute purchasing volume simply because its own end-market demand has grown, without any genuine increase in relational loyalty toward the supplier. The AEP addresses this distinction by measuring whether the buyer intends to allocate a larger relative fraction of its total category spend to the focal supplier, potentially displacing competing vendors. Capturing this relative dimension differentiates genuine relational commitment from passive market-driven volume expansion.

Theoretical Framework

The Anticipated Expansion of Purchases Scale is anchored at the confluence of three dominant theoretical paradigms in organizational behavior and industrial marketing: Transaction Cost Economics, Relational Contracting Theory, and Social Exchange Theory.

Transaction Cost Economics (TCE)

Originating in the works of Ronald Coase and expanded by Oliver E. Williamson, Transaction Cost Economics posits that firms structure their interorganizational governance mechanisms to minimize the sum of production costs and transaction costs. Transaction costs encompass search and information costs, bargaining costs, and policing/monitoring costs associated with opportunism under conditions of bounded rationality and asset specificity. When a supplier demonstrates dependable adherence to contracts and invests in idiosyncratic physical or human assets, the customer’s monitoring and coordination costs decline markedly. As Williamson postulated, when behavioral uncertainty and opportunism hazards abate, buying firms willingly deepen their bilateral exposure. The AEP operationalizes this increased bilateral dependency by capturing the customer’s willingness to concentrate higher transaction volumes with an efficient, trustworthy counterparty.

Relational Contracting Theory and Social Exchange Theory

While TCE emphasizes opportunism mitigation and cost economizing, Social Exchange Theory (pioneered by George Homans and Peter Blau) and Relational Contracting Theory (articulated by Ian Macneil) emphasize the developmental and psychological dimensions of inter-firm governance. Over extended interactions, commercial exchanges foster relational norms, including flexibility, information sharing, and solidarity. Cannon and Homburg (2001) integrated these perspectives by demonstrating that customer firms incur direct costs (e.g., purchase price) and indirect operational costs (e.g., internal inventory management, quality inspection, process adaptation). When supplier behaviors effectively diminish the buyer’s indirect procurement costs, an implicit psychological contract is formed, underpinned by the norm of reciprocity. The buying organization reciprocates value received by granting preferred vendor status and expanding future business allocations, which the AEP measures directly.

Validity

The psychometric integrity of the Anticipated Expansion of Purchases Scale has been verified through multiple validation procedures across varied industrial procurement settings.

Construct and Convergent Validity

In Cannon and Homburg’s (2001) foundational study, survey responses were gathered from purchasing executives across a wide cross-section of manufacturing operations. To establish convergent validity, all scale items were submitted to confirmatory factor analysis (CFA). The factor loadings for all items exceeded the conventional .70 benchmark (ranging between .75 and .89), with all t-values achieving statistical significance at p < .001. The average variance extracted (AVE) exceeded the .50 criterion, verifying that the majority of observed variance stems from the latent construct rather than measurement error.

Discriminant Validity

Discriminant validity was established through the Fornell-Larcker criterion. The square root of the AVE for the AEP construct was found to be significantly greater than its bivariate correlation with all other constructs in the nomological network, including supplier relationship-specific investments, customer adaptation, communication openness, and overall supplier pricing competitiveness. Additionally, nested CFA model comparisons—in which the correlation between AEP and adjacent relational constructs was alternately freely estimated and constrained to unity (1.0)—demonstrated that the unconstrained models exhibited statistically superior chi-square fit, confirming the distinct psychometric identity of the AEP construct.

Predictive and Nomological Validity

Nomological validity was verified through structural equation modeling (SEM) linking the scale to antecedents and structural outcomes. The AEP demonstrated strong, theoretically consistent relationships with reductions in customer acquisition and operational costs. Buying firms reporting substantial reductions in indirect operational costs (via superior technical support and product quality) exhibited significantly higher scores on the AEP (standardized path coefficients typically ranging from .32 to .48, p < .01). Furthermore, longitudinal tracking in subsequent supply-chain studies confirmed that high AEP scores reliably predict longitudinal increases in actual invoiced expenditure and formal single-source contract awards.

Reliability

The AEP exhibits high reliability across diverse empirical investigations in marketing and supply chain logistics:

• Internal Consistency: In the initial validation study by Cannon and Homburg (2001), the scale demonstrated high internal consistency, yielding a Cronbach’s alpha (α) of .85 and a composite reliability (CR) of .86.
• Replication Reliability: Subsequent cross-validation studies applying the AEP in distinct procurement contexts (e.g., European industrial machinery sourcing, automotive original equipment manufacturing, and high-tech component assembly) have routinely reported internal consistency coefficients ranging from .82 to .91, well above the standard psychometric threshold of .70 recommended for organizational research.
• Variance Explained: The extracted construct variance routinely exceeds 65%, demonstrating minimal contamination from idiosyncratic response biases or item-level stochastic noise.

Factor Analysis

Extensive factor-analytic procedures have consistently corroborated the unidimensional structure of the Anticipated Expansion of Purchases Scale when modeled within broader structural equation systems:

Exploratory Factor Analysis (EFA)

Initial principal components analysis and maximum likelihood exploratory factoring with oblique (Promax) rotation yield a single distinct factor characterized by an eigenvalue substantially greater than 1.0 (accounting for over 70% of total item variance). Item cross-loadings against parallel relationship constructs (such as trust, commitment, and opportunism) remain uniformly low (< .25), confirming high factorial purity.

Confirmatory Factor Analysis (CFA)

In full measurement models evaluating the complete suite of buyer-supplier dynamics, the single-factor specification of the AEP exhibits good fit. Across published models utilizing maximum likelihood estimation in AMOS or LISREL, fit indices routinely fall within recommended psychometric thresholds:

• Comparative Fit Index (CFI) > .97
• Tucker-Lewis Index (TLI) > .95
• Root Mean Square Error of Approximation (RMSEA) < .05 (with 90% confidence intervals between .00 and .08)
• Standardized Root Mean Square Residual (SRMR) < .04

Individual standardized factor loadings for the scale items onto the latent AEP construct consistently exceed .75, with statistically significant parameter estimates throughout.

Instrument / Measurement Tool

The structure and operational parameters of the Anticipated Expansion of Purchases Scale are detailed below:

• Test Type: Organizational psychometric assessment tool / Self-report perceptual scale for key informants.
• Target Respondent: Organizational purchasing agents, procurement managers, category directors, or members of the corporate buying center possessing direct purchasing authority for the focal vendor category.
• Administration Format: Standardized paper-and-pencil questionnaire, enterprise computer-assisted web interview (CAWI), or secure digital research portal.
• Scale Structure: Concise multi-item inventory (typically administered as 3 to 4 standardized statements).
• Response Format: Seven-point Likert-type scale anchored by:
  • 1 = Strongly Disagree
  • 2 = Disagree
  • 3 = Somewhat Disagree
  • 4 = Neutral / Neither Agree nor Disagree
  • 5 = Somewhat Agree
  • 6 = Agree
  • 7 = Strongly Agree
• Scoring Protocol: A continuous composite score is generated by calculating the unweighted arithmetic mean across the scale items. Higher numerical scores (e.g., values approaching 7.0) indicate strong strategic intent to expand transaction volumes and increase the supplier’s category share of wallet. Lower scores (e.g., values approaching 1.0) reflect static or declining purchase commitments.
• Administration Time: Approximately 2 to 3 minutes when embedded in an enterprise vendor evaluation survey.

Permissions & Fee and Test Year

The Anticipated Expansion of Purchases Scale was formally introduced in 2001 within the following publication:

Cannon, J. P., & Homburg, C. (2001). Buyer–supplier relationships and customer firm costs. Journal of Marketing, 65(1), 29–43.

The conceptual framework and specific survey items as originally published are intellectual property protected under copyright held by the American Marketing Association (AMA) and distributed through SAGE Publications. While the scale is widely accessible in published form for academic, non-commercial research, investigators conducting formal empirical studies, clinical assessments, or commercial consultancy evaluations are responsible for obtaining formal reprint or reuse permissions via the Copyright Clearance Center (RightsLink) or directly from the publisher. No standardized administrative fee is assessed for independent academic researchers employing the measurement model within peer-reviewed university research.

References

• Cannon, J. P., & Homburg, C. (2001). Buyer–supplier relationships and customer firm costs. Journal of Marketing, 65(1), 29–43. https://doi.org/10.1509/jmkg.65.1.29.18136
• Blau, P. M. (1964). Exchange and power in social life. John Wiley & Sons.
• Fornell, C., & Larcker, D. F. (1981). Evaluating structural equation models with unobservable variables and measurement error. Journal of Marketing Research, 18(1), 39–50. https://doi.org/10.1177/002224378101800104
• Homburg, C., & Rudolph, B. (2001). Customer satisfaction in industrial markets: Dimensional and holistic approaches. Journal of Business Research, 52(1), 15–33. https://doi.org/10.1016/S0148-2963(99)00075-5
• Macneil, I. R. (1980). The new social contract: An inquiry into modern contractual relations. Yale University Press.
• Williamson, O. E. (1985). The economic institutions of capitalism: Firms, markets, relational contracting. Free Press.

Items of the Scale