HUMAN LONGEVITY 51 



the climb, while the 1930 Ladder at the same point will hold 

 almost three-quarters of the starters. 



Ill 



In these pictures we see graphically how the prospects for 

 the duration of the journey of life have been altered in the last 

 fifty years or so, and for the better. The improvement has been 

 great, and much credit is due to the medical and public health 

 professions for the part they have played in bringing it about. 

 But the pictures of the Ladders do not make it entirely clear 

 just how and wherein the improvement has been made. They 

 give rather a broad general impression of the whole effect. In 

 order to apprehend more clearly a very important, and often 

 overlooked, point about this average improvement in the dura- 

 tion of the individual's life resort must be had to some other pic- 

 tures, shown in Figure 3. 



These are pictures of Life Ladders too, but of only their upper 

 parts. Suppose we consider what happened subsequently to 

 10,000 white males who got to the forty-year rung of the 

 1890 Ladder in comparison with 10,000 who will get to the 

 same rung of the 1930 Ladder j and then suppose we make the 

 same comparison between 10,000 who got to the 70-year rung 

 of the 1890 Ladder and an equal number at the same position 

 on the 1930 Ladder. 



It is at once evident from the figure that the duration of the 

 life journey after age 40 for those who have attained that age is, 

 on the average, only slightly longer now than it was in 1890. 

 According to the 1929-31 mortality experience 2.9 per cent 

 of all those (males) reaching forty lived to reach ninety years 

 of age. But the 1890 experience shows that 2.7 percent, or 

 almost as many relatively, did the same then. The gain in the 

 half century for the forty-year old boys is wholly insignificant 

 in any practical point of view. 



The figure further shows that those who attain the age of 

 70 now actually do not do so well relatively, on the average, 

 in the way of further survival to still higher ages as did the 



