Revenue growth from other items, including additional tenant payments to cover costs, such as ground rent or power and fuel costs, included in certain tenant leases (“pass-through”), straight-line revenue and decommissioning.
Due to our diversified communications site portfolio, our tenant lease rates vary considerably depending upon numerous factors, including, but not limited to, tower location, amount, type and position of tenant equipment on the tower, ground space required by the tenant and remaining tower capacity. We measure the remaining tower capacity by assessing several factors, including tower height, tower type, environmental conditions, existing equipment on the tower and zoning and permitting regulations in effect in the jurisdiction where the tower is located. In many instances, tower capacity can be increased with relatively modest tower augmentation capital expenditures.
In general, our tenant leases with wireless carriers have an initial non-cancellable term of at least ten years, with multiple renewal terms. Accordingly, nearly all of the revenue generated by our property operations during the three and nine months ended September 30, 2017 was recurring revenue that we should continue to receive in future periods. Based upon foreign currency exchange rates and the tenant leases in place as of September 30, 2017, we expect to generate nearly $34 billion of non-cancellable tenant lease revenue over future periods, before the impact of straight-line lease accounting. Most of our tenant leases have provisions that periodically increase the rent due under the lease, typically based on an annual fixed escalation (averaging approximately 3% in the United States) or an inflationary index in our international markets, or a combination of both. In addition, certain of our tenant leases provide for pass-through revenue.
The revenues generated by our property operations may be affected by cancellations of existing tenant leases. As discussed above, most of our tenant leases with wireless carriers and broadcasters are multiyear contracts, which typically are non-cancellable; however, in some instances, a lease may be cancelled upon the payment of a termination fee.
Revenue lost from either cancellations or the non-renewal of leases or rent renegotiations historically has not had a material adverse effect on the revenues generated by our property operations. We define churn as tenant billings lost when a tenant cancels or does not renew its lease or, in limited circumstances, when the lease rates on existing leases are reduced. During the nine months ended September 30, 2017, churn represented approximately 2% of our tenant billings.
Demand Drivers. We continue to believe that our site leasing revenue is likely to increase due to the growing use of wireless services globally and our ability to meet the corresponding incremental demand for our communications real estate. By adding new tenants and new equipment for existing tenants on our sites, we are able to increase these sites’ utilization and profitability. We believe the majority of our site leasing activity will continue to come from wireless service providers, with tenants in a number of other industries contributing incremental leasing demand. Our site portfolio and our established tenant base provide us with new business opportunities, which have historically resulted in consistent and predictable organic revenue growth as wireless carriers seek to increase the coverage and capacity of their existing networks, while also deploying next generation wireless technologies. In addition, we intend to continue to supplement our organic growth by selectively developing or acquiring new sites in our existing and new markets where we can achieve our risk-adjusted return on investment objectives.
Consistent with our strategy to increase the utilization and return on investment of our sites, our objective is to add new tenants and new equipment for existing tenants through colocation and lease amendments. Our ability to lease additional space on our sites is primarily a function of the rate at which wireless carriers and other tenants deploy capital to improve and expand their wireless networks. This rate, in turn, is influenced by the growth of wireless services, the penetration of advanced wireless devices, the level of emphasis on network quality and capacity in carrier competition, the financial performance of our tenants and their access to capital and general economic conditions.
Based on industry research and projections, we expect that a number of key industry trends will result in incremental revenue opportunities for us:
In less advanced wireless markets where initial voice and data networks are still being deployed, we expect these deployments to drive demand for our tower space as carriers seek to expand their footprints and increase the scope and density of their networks. We have established operations in many of these markets at the early