[wcoenen]

This would explain negative bond rates down to -0.40%. Because if you need to park a very large amount of euros safely, banks will start to apply that rate to your deposits so it's better to get any rate that is less negative.

But curiously 10y german bund yields have recently hit -0.70%, and a couple other EU countries (France, Netherlands, Belgium) have also dipped below -0.40%.

So it must be more than the negative deposit rate. It's also the QE program which buys bonds (though it's on hold since the start of the year), and the expectation of lower deposit rates, and the expectation of more QE.

[whatok]

I agree with all of this and probably could have phrased my original post better. My main point is that none of this is really possible without ECB rates being set where they are. Successful monetary policy requires multiple tools to be utilized and the deposit rate is the main tool that anchors everything else. QE in itself does not mean rates are going to be lower. You need central bank rates to also be low in order to have lower government rates. Rates didn't suddenly skyrocket after the ECB announced the end of QE.

[wcoenen]

> Rates didn't suddenly skyrocket after the ECB announced the end of QE.

That's because the QE program only stopped increasing the ECB's assets. When bonds that are held by the ECB mature, the equivalent amount in new bonds is still being re-bought.

I don't think negative deposit rates are really needed to have negative bond yields. You only need a bond buyer (e.g. the QE program) who drives up bond prices beyond the face value + all coupons. Negative interest rates were just a natural step in the progression of lower rates, zero rates, negative rates, and QE. The next thing will be some form of helicopter money.

[whatok]

> That's because the QE program only stopped increasing the ECB's assets. When bonds that are held by the ECB mature, the equivalent amount in new bonds is still being re-bought.

Reinvesting maturing proceeds does not produce the same effect as net purchases. One, maturities are lumpy vs regularly scheduled net purchases. There have been rate shocks where idiosyncratic country events happened outside of maturities. Two, while the ECB can basically do whatever it wants, no new net purchases restricts its ability to act in an emergency. Three, size is much smaller.

>I don't think negative deposit rates are really needed to have negative bond yields. You only need a bond buyer (e.g. the QE program) who drives up bond prices beyond the face value + all coupons. Negative interest rates were just a natural step in the progression of lower rates, zero rates, negative rates, and QE. The next thing will be some form of helicopter money.

Note how I didn't mention anything about negative rates in particular; just low rates and that the deposit rate anchors things. Whether rates are negative or not really doesn't matter in isolation. What matters is the spread vs other less risky assets for the goals of the central bank. If a central bank indiscriminately purchases bonds without regard for existing yields or the deposit rate, they will quickly lose control over the market.