Bitcoin isn’t the only asset that could be in a bubble, according to 500 institutional investors surveyed by Natixis. More than three-quarters of institutional investors are concerned that the prolonged period of low interest rates has led to bubbles in one or more asset classes. This is according to a Natixis Investment Managers survey of 500 global investors managing more than $19 trillion of assets combined, including managers of pension funds, endowments, foundations, insurance funds, and sovereign wealth funds.