Data validity is an ongoing concern for life cycle analyses. If LCA conclusions are to be valid, data used in the LCA inventory must accurate and valid, and so, with regard to validity, recent. Moreover, when comparing a pair of LCAs for different products, processes, or services, it is crucial that data of "equivalent" quality are available for the pair being compared. If one of the pair, e.g., a product, has a much higher availability of accurate and valid data, it cannot be justly compared to another product which has lower availability of such data. With regard to the timeliness of data, it has been noted that data validity can be at odds with the time that data-gathering takes. Due to globalization and the pace of research and development, new materials and manufacturing methods are continually being introduced to the market, making it both important and difficult to identify and apply up-to-date information. For instance, in the consumer electronics sector, products such as cell phones may be redesigned as often as every 9 to 12 months, creating a need for rapid, ongoing data collection. As noted above, the inventory in the LCA usually considers a number of stages including: materials extraction, processing and manufacturing, product use, and product disposal. If the most environmentally harmful of these stages can be determined, then impact on the environment can be efficiently reduced by focusing on making changes for that particular phase. For example, the most energy-intensive stage in the LCA of an aircraft or automobile product is during its use, as a result of fuel consumption during the product lifetime. An effective ways to increase fuel efficiency is to decrease vehicle weight; hence, aircraft and automobile manufacturers can decrease environmental impact through replacement of heavier materials with lighter ones (e.g., aluminium or carbon fiber-reinforced elements), all specifications and other costs being equal. Data sources used in LCAs are typically large databases. It is not appropriate to compare two options if different data sources have been used to source the data. Common data sources include: Calculations for impact can then be done by hand, but it is more usual to streamline the process by using software. This can range from a simple spreadsheet, where the user enters the data manually to a fully automated program, where the user is not aware of the source data. Cradle-to-grave is the full Life Cycle Assessment from resource extraction ('cradle') to use phase and disposal phase ('grave'). For example, trees produce paper, which can be recycled into low-energy production cellulose (fiberised paper) insulation, then used as an energy-saving device in the ceiling of a home for 40 years, saving 2,000 times the fossil-fuel energy used in its production.