Does history repeat itself? The only way to get a more precise sample average is to collect more data further back in time. But as we add older data, we gain recision at the expense of introducing potential bias GM: 1925-2000, historical average is 15.5% standard error is 3. 4%:8.7%,22.3%.The interval is still too wide for comfort Moreover, GM is very different from seventy years ago so the current estimate could be contaminated by old dataDoes history repeat itself? ◼ The only way to get a more precise sample average is to collect more data further back in time. But as we add older data, we gain precision at the expense of introducing potential bias. ◼ GM: 1925-2000, historical average is 15.5%, standard error is 3.4%: [8.7%, 22.3%]. The interval is still too wide for comfort. ◼ Moreover, GM is very different from seventy years ago, so the current estimate could be contaminated by old data