Common comparisons published in news reports for construction spending are, from best to worst:
- Current year-to-date vs same period previous year. YTD
- Current month vs previous month. Mo/Mo or MOM
- Current month vs same month last year. Yr/Yr or YOY
- Number of months to current value since last time that value achieved.
In some cases a comparison uses Not Seasonally Adjusted (NSA) dollars and in other cases Seasonally Adjusted Annual Rate (SAAR) dollars. NSA dollars is the actual amount spent within the month. SAAR dollars represents the annual rate that monthly amount would generate based on the normal proportion typical spent within that month. Typical spending is always much higher in summer months than winter to produce the same SAAR.
Year-to-date is the best comparison. It increases in strength as more months are added to the YTD. It is a value that gives a strong indication of growth over the previous year. Comparisons must be made using Not Seasonally Adjusted (NSA) dollars. Although it does lack adjustment for inflation, only one year of inflation is involved. Not adjusting for inflation is explained as the difference between current dollars and constant dollars.
Current month to month (MOM) comparisons are not generally affected by inflation but may not give a clear indication of movement due to monthly fluctuations. Comparisons absolutely must be made using Seasonally Adjusted Annual Rate (SAAR) dollars. It is a gross error to make month to month comparisons using NSA dollars, since there is a normal spending curve that shows the percent of total annual spending can vary considerably from month to month, sometimes by as much as 10%. This variation is accounted for in the SAAR.
When comparing to the same month last year (YOY), the question arises, “Is any big change in YOY caused by the current month performance or by the performance in the same month last year?” Again, YOY is missing adjustment for one year of inflation. Comparison can be NSA or SAAR dollars.
Number of months/years since current value was last achieved is almost always presented as a current dollar comparison. When dealing with cost, because of the long duration often involved it would be much better if it were a constant dollar comparison to account for construction inflation. However, construction inflation may not be readily available and this type of comparison is rarely if ever published using constant dollar comparisons. Comparison should use either entire year total dollars or should use SAAR dollars.
Current dollars = dollars are reported in the value of the year reported 2008=2008$, 2015 = 2015$. 99% of news reports use current dollars and therefore do not account for the influence of inflation.
Constant dollars = all dollars adjusted to represent dollars in the year of comparison. Adjusts for inflation so 2008$ in this case are converted to equivalent 2015$.
It’s not to hard to understand why we need to use constant dollars when you think of it in terms of buying products like food or heating oil. Today heating oil costs $1.90/gallon. In 2008 heating oil cost $3.50/gallon. So, with respect to oil, $350 in 2008 dollars is no different than $190 in 2015 dollars.
In addition to the Year-to-date growth values, here’s two more less common stats for looking at the same information.
Percent change from the last cycle high current$ (contant 2015$)
- Residential – Q1 2006 $390b vs $$680b -43% (-50%)
- Nonresidential Buildings – Q1 2008 $392b vs $$439b -11% (-22%)
- Nonbuilding Infrastructure – Q1 2008 $298b vs $$286b +4% (-10%)
Percent change from the recent recession low current$ (contant 2015$)
- Residential – Q1 2011 $390b vs $$239b +64% (+48%)
- Nonresidential Buildings – Q1 2011 $392b vs $$267b +49% (+35%)
- Nonbuilding Infrastructure – Q1 2008 $298b vs $$243b +22% (+13%)
Constant dollars makes a huge difference in the statistics. Just take a look at Nonresidential buildings. Current dollars would indicate we are now only 11% below the previous high and we’ve had growth of 49% from the recession low. Constant dollars adjusting for inflation shows we are still 22% below the previous cycle high and we’ve had growth of only 35% since the recession lows.
You can find a complete section providing constant dollar cost comparison in my quarterly report. Access the report through the Featured Economic Report tab at the top of this blog