Year Percent change (Units) 2014 2.901 2015 3.276 2016 2.947 2017 1.560 2018 0.556 2019 1.092 2020 2.102 2021 3.424 2022 3.981 2023 3.642 2024 3.168 2025 2.728 2026 2.405 2027 2.132 2028 1.847 2029 1.758