STEM help / Calculation framework

Inputs beginning with ‘U’


The unit of connections for a Market Segment (e.g., Customers, Establishments, Homes) or sites for a Location (e.g., Links, Nodes, Cells). Either type a unit or choose from the drop-down list.

The selection has no mathematical effect on the model, but the text is used to label the y-axis on results graphs.

Default: none.


When the Type of a Sensitivity is set to Proportion, determines the proportion by which the value of a parameter is increased (e.g., 1%).

When Type is set to Delta, specifies the fixed amount by which the value of the parameter is increased (e.g., 10,000).

When Type is set to Absolute, specifies the maximum value of the parameter (e.g., 500,000).

See 9.4 Using sensitivities to identify critical model assumptions.

Default: Constant {0.00}.

Usage Cost

The cost of using a Resource per period (as defined by the Cost Period input), in its Calibration Period, charged pro-rata on the basis of the used capacity of the Resource.

For a consumable resource, usage cost is the cost of using one unit, in proportion to its actual usage, and generated in the period when the capacity is used.

Default: 0.0.

Usage Cost Trend

This is applied to the calibration value you set for Usage Cost in the Resource/Costs dialog.

Default: Constant {1.0}.

Usage Tariff

The tariff charged per unit of traffic. For example, if the Traffic Unit is Call Minutes, the Usage Tariff is the tariff charged per minute.

Default: cost independent and Constant {0.0}.

Note: The simple Tariffs dialog just shows the Cost Independent Tariffs, which are also shown in the more detailed Advanced/Cost Dependent Tariffs dialog.

Use Average Connections

A choice of how connections are used to calculate various Service results.

No: end-of-year connections are used for all calculations, maintaining compatibility with versions of STEM prior to STEM 5.0.

Yes: the average number of connections over a year is used to calculate Annual Traffic, as well as Rental and Usage Revenues.

Default: Yes.

Use Global Trends

Determines whether global cost trends are used.

Default: Yes.

Use Slack

A choice governing how any slack capacity should be taken up when demand increases:

Even: slack capacity is taken up evenly across all installed ages of the resource.

Oldest: the oldest capacity is used first.

Newest: the newest capacity is used first.

Default: Even.

User 1, User 2, …

General-purpose time-series inputs, for each of the main types of model element, which can be referenced in formulae, and also in the definitions of derived results.

These fields do not affect the model results directly.

See 9.1 Extending the STEM data model with user data.

Default: Constant {0.0}.


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