There's a panel in Germany that was in use for 36 years: https://www.presse.uni-oldenburg.de/einblicke/54/files/assets/downloads/page0009.pdf https://www.presse

There's a panel in Germany that was in use for 36 years: https://www.presse.uni-oldenburg.de/einblicke/54/files/assets/downloads/page0009.pdf https://www.presse.uni-oldenburg.de/einblicke/54/files/asset... Efficiency went from 8.55% to 8.2%