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Dispensing days includes week days and
Saturdays but excludes Sundays and Bank Holidays.
Other
Forecasting Methods
As a result of feedback
from stakeholders and our work in developing the PCT
Prescribing Report, we have had several enquiries as
to whether we could assist PCTs with forecasting prescribing
expenditure. Consequently, we have carried out research
into different methods that PCTs could use to forecast
expenditure on drugs. The results of this research showed
that two forecasting methods could be useful to PCTs
in addition to the forecast outturn calculation included
in the PCT Prescribing Report and ePACT.net. A spreadsheet
has been developed for you to calculate your forecast
expenditure for the year and you can download this from
the links below.
Forecasting
Spreadsheet 2008-2009
The two forecasting
methods used in the spreadsheet are the linear trend method
and the moving averages method. The linear trend method
is the simplest of the two and is calculated by drawing
a best fit line through previous data and extrapolating
this line into the future. The moving averages method
smoothes the data in such a way that the effect of random
variation is reduced and the underlying pattern is easier
to see.
The advantage of the
linear trend method is that it is simple to calculate
and understand however, it can be easily skewed by extremes
in expenditure (e.g. expenditure is often high around
October due to prescribing of influenza vaccines. This
peak skews the data and artificially high forecasts are
produced.)
The advantage of the
moving averages method is that the smoothing process produces
more stable forecasts from month to month. The drawback
to this method is that it reacts slower than other methods
to permanent changes to the level of expenditure, for
example policies such as the Pharmaceutical Price Regulation
Scheme and the Generic Prices Review could mean that forecasts
based on old higher prices will be too high. In this case,
additional calculations could be carried out locally to
estimate the impact of such policies and the forecast
adjusted accordingly.
Local prescribing
policies could also affect the forecasts and such policies
need to be taken into consideration when estimating expenditure.
We would welcome your
comments or suggestions about the information and forecasting
methods contained on this page.
E-mail contact: lynn.norris@ppa.nhs.uk
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