Income volatility is studied as a component of economic insecurity using recent data from the Cross National Equivalence File (CNEF). Techniques from the inequality literature are applied to longitudinal household incomes and we refer to the results as measurements of income insecurity. Using this method we examine (i) cross national differences in average insecurity levels, (ii) the effects of taxes and transfers on the insecurity of different income groups and (iii) the relationships between income insecurity and long-run household income. We find that for pre-government incomes Britain exhibits the highest levels of income insecurity, with the U.S. the lowest. However estimates of insecurity in post-government incomes are highest in the U.S. It is shown that insecurity in market incomes is primarily concentrated around low income families and that this pattern is strongest in Germany and weakest in the U.S. Insecurity in post-government incomes is for the most part found to be unrelated to household income.