The old market adage "Sell in May and go away" has worked pretty well in recent years. "In each of the past three years, stocks have pulled back from May to August," notes UBS's Jonathan Golub in a note to clients. "We believe that unique fundamental factors and events were the cause each year." Unfortunately, Golub is convinced that the data is pointing to yet another sell-off in what he has dubbed "Spring Break IV." "We believe that another spring break is likely to materialize and that now is a good time to begin dialing back on risk," we writes.