</code>, how future years should be inflated. 
The future wage series can be provided in two ways: 
(1) a single value, to be the assumed rate of wage inflation in years beyond the known series, or 
(2) a <code>data.table</code> with two variables, <code>fy_year</code> and <code>r</code>. If (2), 
the variable <code>fy_year</code> must be a vector of all financial years after the last financial year in the (known) wage series and the latest <code>to_fy</code> <strong>inclusive</strong>.
The variable <code>r