2009 said that food production would have to increase by 70% over the next 40 years, and food production in the developing world would need to double to feed a projected population increase from 7.8 billion to 9.1 billion in 2050. The effects of global warming (floods, droughts, and other extreme weather events) are expected to negatively affect food production, with different impacts in different regions. The FAO also said the use of agricultural resources for biofuels may also put downward pressure on food availability. The more recent emergence of bio-energy with carbon capture (BECCS) as a prevalent 'negative emissions' strategy for reaching Paris Climate Accord goals is another such pressure. Evidence in support Research indicates that technological superiority and higher land productivity had significant positive effects on population density but insignificant effects on the standard of living during the time period 1–1500 AD. In addition, scholars have reported on the lack of a significant trend of wages in various places over the world for very long stretches of time. In Babylonia during the period 1800 to 1600 BC, for example, the daily wage for a common laborer was enough to buy about 15 pounds of wheat. In Classical Athens in about 328 BC, the corresponding wage could buy about 24 pounds of wheat. In England in 1800 AD the wage was about 13 pounds of wheat. In spite of the technological developments across these societies, the daily wage hardly varied. In Britain between 1200 and 1800, only relatively minor fluctuations from the mean (less than a factor of two) in real wages occurred. Following depopulation by the Black Death and other epidemics, real income in Britain peaked around 1450–1500 and began declining until the British Agricultural Revolution. Historian Walter Scheidel posits that waves of plague following the initial outbreak of the Black Death throughout Europe had a leveling effect that changed the ratio of land to labor, reducing the value of the former while boosting that of the latter, which lowered economic inequality by making employers and landowners less well off while improving the economic prospects and living standards of workers. He says that "the observed improvement in living standards of the laboring population was rooted in the suffering and premature death of tens of millions over the course of several generations." This leveling effect was reversed by a "demographic recovery that resulted in renewed population pressure." Robert Fogel