It is well known that government bond yields in advanced economies tend to be closely linked to nominal GDP growth. It is less well known that this relationship has been unsteady over time. Economic theory (as in Solow Growth Model) postulates that bond yields should equal nominal GDP growth, and many market participants concur. But in reality the relationship between government bond yields and nominal GDP (we refer to this differential as the “yield -GDP gap”) has experienced six distinct regime shifts since the beginning of the 20th century. Our analysis shows that two factors best explain these regime shifts: 1) the trend in inflation, and 2) the pace of aggregate debt growth (in relation to the size of the economy). In other words, the faster debt grows relative to GDP, the higher the bond yields for a given pace of nominal GDP growth. And the lower inflation has been in the prior period, the lower the yield-GDP gap will be. At present, when taking into account a likely acceleration in debt to GDP growth which would contribute to structurally higher rates, and the (partially offsetting) impact of low inflation over the last decade, we estimate that over the next 5 years, the average yield-GDP gap will rise 80 basis points, suggesting the U.S. 10-year yield could reach 3.5-3.7% by 2023.