national multiple family submetering and allocation billing program ...

analysis, intended to control best for competing explanations for water use differences among
properties with different billing types, included properties with annual average per unit water
usage that was outside of larger sample parameters. With such a small sample of pairs, the
selection of a few properties with atypically high or low water use is always a possibility.
Among the in-rent and RUBS matched pairs, the in-rent water usage was uncommonly high, at
an average of 66 kgal per unit per year compared to 53 kgal per unit per year in the largest
property sample and the RUBS use was slightly low at an average of 48 kgal per unit per year
compared to 52 kgal per unit per year in the largest property sample.
Since the researchers were blind to water use when selecting the sample, there could be
no a priori control of abnormal water use. It seems that the exceptionally high water use in the
in-rent properties matched to the RUBS properties most likely is the reason that this small
matched-pair analysis shows a savings with RUBS. Just as it would be possible to find a small
group of people whose reaction to a placebo pill would seem to help them recover quickly from
the flu, we would not wish to conclude that the pill was, in fact, effective based on those limited
findings when a larger study showed no such impact. Because the other analyses in this chapter
where sample sizes were bigger and statistically controlled showed no water savings associated
with RUBS, it is concluded that this small sample finding of a RUBS effect is most likely
spurious.
Pre/Post Billing Conversion
The pre/post billing conversion analysis aimed to compare water use at the same property
before and after a separate billing system was implemented. By keeping the building constant,
the number of factors that could influence water use at a property are kept to a minimum.
Through the manager survey data, any property that had changed from an in-rent system
to a separate billing system was identified, along with the year of the conversion. Forty-six such
properties were identified that had made such a change in 2000 or in 2001, and for which water
use data were available in years both before and after the conversion year. To avoid including
the transitional period of conversion, the water data from the year of conversion was excluded.
Of the 46 properties identified, 39 had switched to RUBS, 1 to a hot water hybrid system,
and 6 to submetering. The average annual water use before and after conversion for these
properties is shown in Figure 5.18.
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