In four books written from 1921 to 1934, Soddy carried on a "campaign for a radical restructuring of global monetary relationships",[21] offering a perspective on economics rooted in physics – the laws of thermodynamics, in particular – and was "roundly dismissed as a crank".[21] While most of his proposals – "to abandon the gold standard, let international exchange rates float, use federal surpluses and deficits as macroeconomic policy tools that could counter cyclical trends, and establish bureaus of economic statistics (including a consumer price index) in order to facilitate this effort" – are now conventional practice, his critique of fractional-reserve banking still "remains outside the bounds of conventional wisdom" although a recent paper by the IMF reinvigorated his proposals.[21][22] Soddy wrote that financial debts grew exponentially at compound interest but the real economy was based on exhaustible stocks of fossil fuels. Energy obtained from the fossil fuels could not be used again. This criticism of economic growth is echoed by his intellectual heirs in the now emergent field of ecological economics.[21]