(a)

where institutions used the historical method set out in Article 8 for determining the downward and upward calibrated shock of that non-modellable risk factor and the extreme scenario of future shock is the downward calibrated shock, they shall calculate the estimate of the tail parameter in accordance with the following formula:

where:

—

;

—	represents the i-th smallest return in the time series Ret;

—	denotes the integer part of ;

—	is the estimate of the left-tail expected shortfall for the time series Ret calculated in accordance with Article 11(1);

(b)

where institutions used the historical method set out in Article 8 for determining the downward and upward calibrated shock of that non-modellable risk factor and the extreme scenario of future shock is the upward calibrated shock, they shall calculate the estimate of the tail parameter in accordance with the following formula:

where:

—

;

—	represents the i-th smallest return in the time series  ;

—	denotes the integer part of ;

—	is the estimate of the right-tail expected shortfall for the time series Ret calculated in accordance with Article 11(2);

(c)