In 2009-2011, the total volume declared (and paid) under the general regime was only 33% of the volume granted. A water entitlement can expire if the total volume of water granted has not been used in two consecutive years without explanation.19 Since 2011 the water title-holder can pay a guarantee fee {cuota de garantid) to avoid the expiration of the water entitlement. The aim of this mechanism is to encourage title-holders that do not intend to use the water to give back their titles. The rationale is that unused entitlements generate opportunity costs for society: water that is allocated but not used could be used in other activities and generate social benefits.