How to interpret negative bond yield quote

A negative yield just means you paid $101 to receive $100 in the future. Negative yields are occurring for reasons including but not limited to an expectation that yields will be even lower in the future.

Unless you are well over the insured limit for savings accounts in your country negative yields mean nothing to you.

To expand, YTM (Yield to Maturity) is a complicated calculation particularly when you venture in to multi year bonds. As an example you buy a 10 year, $100 bond with a 5% coupon for $99 (Lets just assume that the coupon payments are once per year for simplicity sake.)

In year 1, pay $99 you recieve $5 in coupon payments. So your yield in year 1 is 5.05% (5/99 = 0.050505)

The future years are a little different because in year 2 you receive another $5, but this time it took 2 years to receive. In year 3 it's the same story, another $5 coupon payment and so on until year 10 when you receive $105; the face amount and final coupon payment. YTM calculates a present value of all of this. It's not just one simple formula. IRR (Internal Rate of Return) is another sort of long term cash flow type return calculation that can be reasonable for bond comparisons.

Buying bonds after they've been issued adds the complicating factor of pre-paying accrued coupon payments. If you were to buy this bond exactly six months in to the third year you the seller may want the $2.50 of the $5 coupon payment that has accrued. Now the bond only has 6.5 years remaining and you've included $2.50 in your purchase price that's really only applicable to the first year's coupon payment both of these factors will impact the YTM.

The yield represents the present value of the coupons and the redemption value, relative to the current price. In order to calculate the yield, you need to know the expected future interest rates in order to discount the coupons to their value in today's currency.

When a bond has a negative yield, it means that you are paying more today for the bond than you get back in coupons (indeed in this case, you're paying 134.67 for about 132.50 in future payments (coupons and principal). Financially, it measn that you're paying the bank/government/company to hold your money for you.