The difference looks fairly consistent: Febuary 1995: U6 is 183% of U3. Febuary 2000: U6 is 175% of U3. Febuary 2004: 173% Febuary 2006: 155% Febuary 2007:

The difference looks fairly consistent: Febuary 1995: U6 is 183% of U3. Febuary 2000: U6 is 175% of U3. Febuary 2004: 173% Febuary 2006: 155% Febuary 2007: 182% March 2008: 178% Febuary 2009: 183% March 2010: 172% Febuary 2011: 177% Febuary 2012: 180% March 2013: 184% Febuary 2014: 188% There quite a bit of variance, but it seems to be seems to have been consistently in the 170-185%, with a few outliers.