Variety and Inventory Trade-off in Retailing: An Empirical Study

38 Pages Posted: 22 Mar 2021

See all articles by Gurhan Kok

Gurhan Kok

Koc University

A. Serdar Şimşek

Jindal School of Management - The University of Texas at Dallas

Date Written: February 24, 2021


We investigate the trade-off between variety and inventory in retailing using a proprietary data set from a bookstore chain. In general, more variety is expected to generate higher traffic to store and higher conversion for incoming customers. Another argument is that too much variety reduces sales due to the confusion it creates in the customers’ minds (choice paradox). Higher variety also implies lower inventory per product due to limited shelf space in the stores. Hence, a critical question for a retailer is to determine where their stores are currently positioned on the variety-sales curve, and whether or not they should increase/decrease variety by extending/cutting the long tail of slow-moving products. We consider number of subcategories, number of products in a subcategory, average inventory per product, and inventory dispersion as measures of, respectively, macro variety, micro variety, inventory depth, and inventory policy effectiveness. We exploit the differences between stores and variations over time to investigate the net impact of variety and inventory on sales of total category and of top-selling products. We control for store traffic and seasonality, and introduce instrumental variables to control for endogeneity of variety and inventory. We find that both micro and macro variety increase total category sales. Further, variety increases sales of the top-selling products as well—a somewhat surprising positive effect of presenting the long-tail of products to customers. We also demonstrate how a retailer can significantly increase its revenue by optimally swapping shelf spaces across product categories based on the estimated category-specific variety effects.

Keywords: product variety, inventory, retail, long-tail products, empirical operations

Suggested Citation

Kok, Gurhan and Şimşek, A. Serdar, Variety and Inventory Trade-off in Retailing: An Empirical Study (February 24, 2021). Available at SSRN: or

Gurhan Kok

Koc University ( email )

Rumelifeneri Yolu
34450 Sar?yer
Istanbul, 34450

A. Serdar Şimşek (Contact Author)

Jindal School of Management - The University of Texas at Dallas ( email )

800 W Campbell Rd, SM 30
Richardson, TX 75080
United States


Do you have a job opening that you would like to promote on SSRN?

Paper statistics

Abstract Views
PlumX Metrics