as increased employment density and improved public transportation. Third, that higher density, mixed-use developments would produce both direct reductions in emissions (from less driving), and indirect reductions (such as from lower amounts of materials used per housing unit, higher efficiency climate control, longer vehicle lifespans, and higher efficiency delivery of goods and services). Fourth, that although short-term reductions in energy use and emissions would be modest, that these reductions would become more significant over time. Fifth, that a major obstacle to more compact development in the United States is political resistance from local zoning regulators, which would hamper efforts by state and regional governments to participate in land-use planning. Sixth, the committee agreed that changes in development that would alter driving patterns and building efficiency would have various secondary costs and benefits that are difficult to quantify. The report recommends that policies supporting compact development (and especially its ability to reduce driving, energy use, and emissions) should be encouraged. An economic theory that has been proposed as a remedy is the introduction of a steady state economy. Such a system could include a tax shifting from income to depleting natural resources (and pollution), as well as the limitation of advertising that stimulates demand and population growth. It could also include the institution of policies that move away from globalization and toward localization to conserve energy resources, provide local jobs, and maintain local decision-making authority. Zoning policies could be adjusted to promote resource conservation and eliminate sprawl. Since aviation relies mainly on jet fuels derived from crude oil, commercial aviation has been predicted to go into decline with the global oil production. Mitigation To avoid the serious social and economic implications a global decline in oil production could entail, the Hirsch report emphasized the need to find alternatives, at least ten to twenty years before the peak, and to phase out the use of petroleum over that time. This was similar to a plan proposed for Sweden that same year. Such mitigation could include energy conservation, fuel substitution, and the use of unconventional oil. The timing of mitigation responses is critical. Premature initiation would be undesirable, but if initiated too late could be more costly and have more negative economic consequences. Global annual crude oil production (including shale oil, oil sands, lease condensate and gas plant condensate but excluding liquid fuels from other sources such as natural gas liquids, biomass and