Year Percent change (Units) 2013 2.800 2014 1.300 2015 0.913 2016 0.024 2017 3.957 2018 4.266 2019 4.517 2020 4.304 2021 4.620 2022 6.785 2023 6.104 2024 4.800 2025 3.900 2026 3.600 2027 3.400 2028 3.200 2029 3.000