pre_text: 21 Share-based payments (a) Performance rights The performance rights plan was established by the Board of Directors to provide long-term incentives to the Group’s Senior Executives based on total shareholder returns (TSR) taking into account the Group’s financial and operational performance. Under the Plan, eligible participants may be granted performance rights on terms and conditions determined by the Board from time to time. Performance rights were granted during the course of FY17, FY18 and FY19. The vesting conditions for grants relate to TSR exceeding the ASX 200 Accumulation Index over the measurement period. Vesting of the rights will be tested on or around the day following the release of each of the annual results for the years ended 30 June 2019, 2020 and 2021 respectively. Performance rights are granted by the Company for nil consideration. The Board has discretion to determine if the value will be provided in shares, cash or a combination of shares and cash. Rights granted under the plan carry no dividend or voting rights. The fair value of the rights at the date of valuation was determined using the Black-Scholes Option Pricing Model to be equal to the volume weighted-average price (VWAP) ending on the day before the grant date, less the dividends expected over the period from the expected grant date to the completion of the measurement period, adjusted for the expected probability of achieving the vesting conditions.
table: 30 June 2019 30 June 2019 30 June 2018 30 June 2018
table: Number of Rights Average Fair Value Number of Rights Average Fair Value
table: Opening balance 2,948,960 $1.87 3,460,195 $1.26
table: Granted during the year 828,285 $3.07 762,577 $3.32
table: Vested during the year (1,307,885) $1.19 (1,273,812) $1.09
table: Forfeited during the year - $0.00 - $0.00
table: Closing balance 2,469,360 $2.64 2,948,960 $1.87
question: Analyse this data from a financial earnings document. What was the average difference between number of rights in opening and closing balance for both years?