# UPD applying the 2 percent rule

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The 2% stability threshold is the criterion to decide whether the value of the reference area of a parcel (“referenceArea” attribute) has to be updated after a geometry operation or measurement. The area values that can be derived from the geometric representation is compared to the value of the reference area recorded in LPIS. A technical tolerance of 2% is applied for the ratio of the two area values. When the difference of the ratio is bigger than 2%, the reference area value of the parcel has to be updated.

Member States should ensure that the maximum eligible areas for the relevant schemes and support measures per reference parcel is correctly quantified within a margin of maximum 2% (the 2% stability threshold), by taking into account the outline and condition of the reference parcel. This 2% stability threshold does not apply to any clear change. It only applies when parcels did not change in reality but the change is caused by delineation differences due to fussy boundaries. In those cases changes compared to the existing parcel up to 2% do not necessarily have to be processed as they are caused by the outline and condition of reference parcels.

The topic is also relevant to decide whether a reported anomaly, only based on area values without other source data, needs to be processed at all.

Measures should be taken to propagate the eventually updated reference area value to the other subsystems of IACS. In particular, it should appear in the pre-printed form for the next application year.

Figure 12: Application of the 2% stability threshold criterion

To apply the 2% stability rule:

1. Start by retrieving the reference area of the parcel, which is available as attribute of the ReferenceParcel feature type
2. Retrieve the area that has been determined/measured/captured in course of update process (reported, changed as a result of new geometry insertion, or applying a new pro-rata class).
3. Calculate the ratio between determined area from the previous step and reference area recorded in IACS to check the area correctness.
4. Control the area correctness ratio: If the area correctness ratio is between 0.98=< ratio=< 1.02, you can choose not to change the reference area. Else, update the reference area in LPIS with the area determined.

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