vehicle safety. In addition, various manufacturers have issued stop sale notices in relation to certain recalls that require that we retain vehicles until the recall can be performed. For certain airbag recalls, these required parts are currently unavailable. While servicing recall vehicles yields parts and service revenue to us, the inability to sell a significant portion of our vehicles could increase our costs and have an adverse effect on our results of operations if a large number of our vehicles are the subject of simultaneous recalls, or if needed replacement parts are not in adequate supply.
Vehicle requirements. Federal and state governments in our markets have increasingly placed restrictions and limitations on the vehicles sold in the market in an effort to combat perceived negative environmental effects. For example, in the U.S., automotive manufacturers are subject to federally mandated corporate average fuel economy standards which will increase substantially through 2025. Furthermore, numerous states, including California, have adopted or are considering regulations requiring the sale of specified numbers of zero-emission vehicles. Significant increases in fuel economy requirements and new federal or state restrictions on emissions on vehicles and fuels in the U.S. could adversely affect prices of and demand for the new vehicles that we sell. With respect to our retail commercial truck dealerships, stricter fuel consumption and emissions standards have been enacted for model year 2014 through 2018 heavy-duty trucks. Similar tighter standards have been proposed for later years. These and other new standards may adversely affect the prices of and demand for the trucks that we sell.
Franchise laws in the U.S. In the U.S., state law generally provides protections to franchised vehicle dealers from discriminatory practices by manufacturers and from unreasonable termination or non-renewal of their franchise agreements. In a recent forum, the U.S. Federal Trade Commission questioned the efficacy of these laws. If these franchise laws are repealed or amended, manufacturers may have greater flexibility to terminate or not renew our franchises. Franchised automotive dealers in the European Union operate without such protections.
Changes in law. New laws and regulations at the state and federal level may be enacted which could materially adversely impact our business. For example, in 2013, a ballot initiative in California titled the California Car Buyers Protection Act was proposed that would have eliminated our ability to be compensated for assisting in financing customer vehicle purchases, among other matters. In addition, representatives from the federal government have proposed a tax on the value of imported foreign-sourced vehicles. As we sell a large number of such vehicles, if any such proposal ultimately led to higher consumer prices for these vehicles, we would be adversely affected. If these initiatives or other adverse changes in law were to be enacted, it could have a significant and adverse effect on us.
Environmental regulations. We are subject to a wide range of environmental laws and regulations, including those governing: discharges into the air and water; the operation and removal of storage tanks; and the use, storage and disposal of hazardous substances. In the normal course of our operations we use, generate and dispose of materials covered by these laws and regulations. We face potentially significant costs relating to claims, penalties and remediation efforts in the event of non-compliance with existing and future laws and regulations.
Accounting rules and regulations. The Financial Accounting Standards Board is currently evaluating several significant changes to GAAP in the U.S., and has recently issued new guidelines for revenue recognition and lease accounting. Upon adoption and effectiveness, such changes could significantly affect our reported financial position, earnings and cash flows. See the disclosure provided under “Recent Accounting Pronouncements” in Part II, Item 8, Note 1 of the Notes to our Consolidated Financial Statements. In addition, changes to lease accounting could affect PTL customers’ decisions to purchase or lease trucks, which could adversely affect their business if leasing becomes a less favorable option.
Related parties. Our two largest stockholders, Penske Corporation and its affiliates (“Penske Corporation”) and Mitsui & Co. and its affiliates (“Mitsui”), together beneficially own approximately 58% of our outstanding common stock. The presence of such significant shareholders results in several risks, including:
Our principal stockholders have substantial influence. Penske Corporation and Mitsui have entered into a stockholders agreement pursuant to which they have agreed to vote together as to the election of our directors. As a result, Penske Corporation has the ability to control the composition of our Board of Directors, which may allow it to control our affairs and business. This concentration of ownership, coupled with certain provisions contained in