Helmut Melzer
Rayuwar rayuwa ta karu cikin sauri tun daga fadakarwa. A farkon 19. A ƙarni na 19, ya fara ƙaruwa a cikin ƙasashe masu masana'antu, yayin da ya ragu a sauran ƙasashe. A cikin shekarun da suka gabata, rashin daidaituwa na duniya ya ragu. Tun daga shekara ta 1900, matsakaicin rayuwar rayuwar duniya (mai hoto) ya ninka ninki biyu kuma yanzu yana tsaye a kusan shekaru 70.
Alamar kiwon lafiya ita ce tsawon rayuwar mutum zuwa shekaru. A shekara ta 1845, har yanzu akwai bambance-bambance masu yawa: tsammanin rayuwa ga jarirai ya kasance shekaru 40 da kuma shekaru 70 masu shekaru 79. A yau wannan kewayon ya fi ƙanƙanta - daga 81 zuwa 86. Wannan saboda yiwuwar mutuwa a ƙarami yana raguwa koyaushe. "Daidaituwar rayuwa" ya ƙaru ga duka mutane.
