Financial Models built to the FAST standard have more unique formulae than other financial models, but are better built. In this article, I discuss why a good model should not be more expensive to model audit.

1. Model Audit - is a good model more expensive to
audit?
Andy Hucknall – Navigant Consulting
08/07/2009
There have been discussions recently on the client forum of Financial
Mechanics as to whether building a financial model to best practice leads to
an increase in the cost of the model audit. This may sound counter-intuitive
at first, but let me explain why this discussion has arisen.</P< span>
Financial Mechanics, a financial modelling specialist, is a member of the FAST
Modelling Alliance, with 'FAST', being:
• FLEXIBLE - model design and modelling techniques must allow models to be
adapted easily and quickly when new information becomes available
• ACCURATE - models must reflect key business assumptions directly and
faithfully without being over-built or cluttered with unnecessary detail
• STRUCTURED - rigorous consistency in layout and organisation is essential to
retain a model's logical integrity over time, particularly as a model's author
may change
• TRANSPARENT - modelling approach is founded on simple, clear calculations
that can be understood by other modellers and non-modellers alike
Financial models built to best practice have formulae that are consistent across a row
of the model, and often across a whole block. The formula on the left of the row, or
the top left of the block, is said to be the unique formula. A model auditor is, thus,
able to review the unique formula rather than every formula in a row or block,
considerably reducing the workload and cost.
What the FAST methodology advocates is simplicity in the formulae. Where a non-
FAST model may have formulae incorporating multiple logic tests, FAST advocates
short, simple, direct and readily understood formulae. The result is that complicated,
multiple logic formulae are written as separate, linked formulae with a single logic test
in each formula.

2. One of the consequences of the FAST methodology is, thus, an increased number of
unique formulae. This debate is, therefore, confined to FAST and non-FAST financial
models that are built with 'left-right' and 'top-down' consistency, and not between
FAST methodology and badly structured models.
The question on the Fi-Mech forum was "Does the FAST Method drive up model audit
costs?" on the premise that the number of unique formulae is greater. On the
assumption that the number of unique formulae is greater, yet the risk of material
errors should be lower, is would seem perverse that the model audit cost should go
up.
There are two things that the model auditor can take into account to offset the
increased number of formulae:
• complexity factors
• capability risk
Complexity Factors
The complexity factor is a measure of how complicated a formula is, and from that, an
assessment can be made as to how long a formula takes to review - the greater the
complexity, the greater the time.
Many model audit software packages provide an assessment of the model in terms of
the number of unique formulae, and the complexity of each formula.
A model built using the FAST method is likely have lower complexity factor formulae,
although more of them, than other models. Whether these two elements offset will
depend on individual circumstances.
Capability Risk
The terminology "Capability Risk" came from Gavin Townshend, head of financial
modelling at John Laing plc. It is a good way of expressing how a model auditor will
assess a financial model beyond the statistics of unique formulae and complexity
factors.
Using Gavin's words, is "the more robust a client's own internal review processes are
(e.g. running sensitivity tests and analysing the results, commercial sense checking,
etc.) and the more capable the client's own people are at performing such tasks, the
lower the risk of significant model errors", and therefore, the lower the Capability Risk

3. The assertion is that if a client's, or their advisor's, quality assurance procedures in
building a financial model are better, there is a lower risk of material errors in the
financial model.
As the model auditor uses a risk-based approach to planning and undertaking the
model audit, if the Capability Risk is lower, then the amount of work needed to be
undertaken by a model auditor to manage the risk should be lower, and hence, less
costly.
Combination
The building of a financial model to FAST modelling standards in itself will, other
things being equal, lead a model auditor to assess the capability risk to be lower.
Even if the combination of more unique formulae, but at a lower complexity factor,
leads to an increased total length of time to undertake the detailed 'bottom up' review
of each unique formulae, the reduced capability risk will mean less time is needed to
undertake the 'top down' analysis.
It should be noted that the detailed 'bottom up' review of unique formulae is less risky
than the 'top down' analysis, and hence can be undertaken by less senior, and hence,
lower cost, staff.
So even if the time required for 'bottom up' review is marginally longer for FAST
method built financial models, the extra cost is more than offset by the time saving,
at higher hourly rates, in 'top down' analysis.
To reiterate from my earlier article "Model audit - do you know what risk you are
taking on?" (IJ Online, 18 May 2009), the 'top down' analysis will include:
• the re-performance of key calculations based upon the project's
documentation
• analytical review of trends in key outputs
• sensitivity analysis
• commercial sense checking
The amount of time budgeted for 'top down' analysis is a judgemental assessment by
the model auditor based upon experience, of which Capability Risk is a major
influence.
Proper planning (and risk assessment) prevents poor performance (and mitigates the
risk of missing material errors)

4. As with the planning of a statutory audit, the amount of work undertaken is
dependent on the assessment of the risk of a material error. The same applies to
model auditing, and thus, the lower the capability risk, the lower the amount of work
that needs to be undertaken to mitigate the risk of material errors.
This highlights the need for proper risk assessment in planning the model audit, and
advantages of the planning being undertaken by experienced model auditors, ideally a
qualified accountant with statutory audit experience.
Summary
So to answer the question "Does the FAST Method drive up model audit costs?" My
answer would be that it shouldn't do.
More than that, reducing the Capability Risk by building a financial model to best
practice should reduce the cost and financial risk to the client themselves as the
model will be easier to update and optimise in the run up to financial close with less
likelihood of material error.
Author: Andy Hucknall is an associate director at Navigant Consulting. To contact
him, click here...