Imagine a game in which you roll a six-sided dice and win a number of dollars equal to the score. So a one gets you $1, a two gets $2 and so on. How much should you pay to play?

On Feb. 11, the firm unveiled two new bond ETFs designed to provide exposure to the short end of the U.S. Treasury yield curve – the Vanguard Ultra-Short Treasury ETF (ticker: VGUS) and the Vanguard 0 ...