Transportation is therefore of particular interest to those seeking to mitigate the effects of peak oil. Although demand growth is highest in the developing world, the United States is the world's largest consumer of petroleum. Between 1995 and 2005, US consumption grew from per day. China, by comparison, increased consumption from per day in the same time frame. The Energy Information Administration (EIA) stated that gasoline usage in the United States may have peaked in 2007, in part because of increasing interest in and mandates for use of biofuels and energy efficiency. As countries develop, industry and higher living standards drive up energy use, oil usage being a major component. Thriving economies, such as China and India, are quickly becoming large oil consumers. For example, China surpassed the United States as the world's largest crude oil importer in 2015. Oil consumption growth is expected to continue; however, not at previous rates, as China's economic growth is predicted to decrease from the high rates of the early part of the 21st century. India's oil imports are expected to more than triple from 2005 levels by 2020, rising to per day. Population Another significant factor affecting petroleum demand has been human population growth. The United States Census Bureau predicts that world population in 2030 will be almost double that of 1980. Oil production per capita peaked in 1979 at 5.5 barrels/year but then declined to fluctuate around 4.5 barrels/year since. In this regard, the decreasing population growth rate since the 1970s has somewhat ameliorated the per capita decline. Economic growth Some analysts argue that the cost of oil has a profound effect on economic growth due to its pivotal role in the extraction of resources and the processing, manufacturing, and transportation of goods. As the industrial effort to extract new unconventional oil sources increases, this has a compounding negative effect on all sectors of the economy, leading to economic stagnation or even eventual contraction. Such a scenario would result in an inability for national economies to pay high oil prices, leading to declining demand and a price collapse. Supply Defining sources of oil Oil may come from conventional or unconventional sources. The terms are not strictly defined, and vary within the literature as definitions based on new technologies tend to change over time. As a result, different oil forecasting studies have included different classes of liquid fuels. Some use the terms "conventional"