of world trade were developed, unemployment was shown to reduce inflation, following the Phillips curve, or to decelerate inflation, following the NAIRU/natural rate of unemployment theory since it is relatively easy to seek a new job without losing a current job. When more jobs are available for fewer workers (lower unemployment), that may allow workers to find the jobs that better fit their tastes, talents and needs. As in the Marxian theory of unemployment, special interests may also benefit. Some employers may expect that employees with no fear of losing their jobs will not work as hard or will demand increased wages and benefit. According to that theory, unemployment may promote general labour productivity and profitability by increasing employers' rationale for their monopsony-like power (and profits). Optimal unemployment has also been defended as an environmental tool to brake the constantly-accelerated growth of the GDP to maintain levels that are sustainable in the context of resource constraints and environmental impacts. However, the tool of denying jobs to willing workers seems a blunt instrument for conserving resources and the environment. It reduces the consumption of the unemployed across the board and only in the short term. Full employment of the unemployed workforce, all focused toward the goal of developing more environmentally-efficient methods for production and consumption, might provide a more significant and lasting cumulative environmental benefit and reduced resource consumption. Some critics of the "culture of work" such as the anarchist Bob Black see employment as culturally overemphasized in modern countries. Such critics often propose quitting jobs when possible, working less, reassessing the cost of living to that end, creation of jobs that are "fun" as opposed to "work," and creating cultural norms in which work is seen as unhealthy. These people advocate an "anti-work" ethic for life. Decline in work hours As a result of productivity, the work week declined considerably during the 19th century. By the 1920s, the average workweek in the US was 49 hours, but it was reduced to 40 hours (after which overtime premium was applied) as part of the 1933 National Industrial Recovery Act. During the Great Depression, the enormous productivity gains caused by electrification, mass production, and agricultural mechanization were believed to have ended the need for a large number of previously-employed workers. Remedies Societies try a number of different measures to get as many people as possible into work, and various societies have experienced