Item 2. Properties

As of December 31, 2018, we owned or had ownership interests in 1,111 operating stores. Of these stores, 878 are wholly-owned, four are in consolidated joint ventures, and 229 are in unconsolidated joint ventures. In addition, we managed an additional 536 stores for third parties bringing the total number of stores which we own and/or manage to 1,647. These stores are located in 39 states, Washington, D.C. and Puerto Rico. The majority of our stores are clustered around large population centers. The clustering of assets around these population centers enables us to reduce our operating costs through economies of scale. Our acquisitions have given us an increased scale in many core markets as well as a foothold in many markets where we had no previous presence.

As of December 31, 2018, approximately 910,000 tenants were leasing storage units at the operating stores that we own and/or manage, primarily on a month-to-month basis, providing the flexibility to increase rental rates over time as market conditions permit. Existing tenants generally receive rate increases at least annually, for which no direct correlation has been drawn to our vacancy trends. Although leases are short-term in duration, the typical tenant tends to remain at our stores for an extended period of time. For stores that were stabilized as of December 31, 2018, the average length of stay was approximately 15.1 months.

The average annual rent per square foot for our existing customers at stabilized stores, net of discounts and bad debt, was $16.16 for the year ended December 31, 2018, compared to $15.58 for the year ended December 31, 2017. Average annual rent per square foot for new leases was $17.65 for the year ended December 31, 2018, compared to $16.58 for the year ended December 31, 2017. The average discounts, as a percentage of rental revenues, during these periods were 4.1% and 4.0%, respectively.

Our store portfolio is made up of different types of construction and building configurations. Most often sites are what we consider “hybrid” facilities, a mix of both drive-up buildings and multi-floor buildings. We have a number of multi-floor buildings with elevator access only, and a number of facilities featuring ground-floor access only.

The following table presents additional information regarding net rentable square feet and the number of stores by state: