30-year US treasury bond yields reached a high that has not been seen for 2 decades today.
When making financial decisions, your nominal benchmark for a risk-free long-term return is this financial instrument. Of course you have to factor in whether the US currency will actually be able to purchase anything in 30 years, this is all part of the risk equation. On the flip side, if the US Federal Reserve starts to do quantitative easing in the event of the next global depression, your trade will work out very well.
In the meantime, the higher this yield goes, the more pressure there will be on equity pricing.