224 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table II Values of the Measured Parameters Calculated According to Table I At Age 20 At age 70 % Change Indentation 0. 043 cm 0.054 cm 26 Elastic recovery 80.5 % 65.5 % 19 Levarometry (slackness) 0. 037 cm 0.068 cm 84 Surface pH 5.25 5.61 7 In order to see whether the distribution is homogeneous, we present the histograms of Figures 1-4. It is clear that, except for the skin pH (Figure 4), the data are unho- mogeneous with respect to age. In the pH histogram there is no obvious distribution difference between the 20-39 age group and the 40-70 age group, with the exception Distribution of Indentation ø•Age 20-39y: 95 91 95 79 83 74 66 64 50 40 • 75 •50 25 0 ..J! N=446 20 22 24 26 28 30 32 34 •_19 21 23 25 27 29 31 33 35 __,36 Units 60 Units: 0.1 cm Indentation Figure 1. Distribution of indentation. The "young age" (20-39 years) cases are shown by a dotted line. The unbroken line shows the total number of cases.

AGE DEPENDENCE OF SKIN PROPERTIES 225 125 ø•Age 20- 39Y: lOO istribution 0 40 49 73 75 50 25 of Elastic Recovery 74 82 91 81 100 ...[ 55 56 61 66 71 76 81 86 91 -- 60 65 70 75 80 85 90 -- N = 443 % Elastic Recovery Figure 2. Distribution of elastic recovery. The "young age" (20-39 years) cases are shown by a dotted line. The unbroken line shows the total number of cases. of the extremes: pH 4.3 or less, and pH 6.2 or more. From Figures 1, 2 and 3 it is clear that the high values of indentation and levarometry, and the low values of elastic recovery, are more frequent in the high age group. Table III shows the mean and its range of two standard errors of estimation, calculated from the young (20-39) age group. DISCUSSION The correlation coefficients found by us are within those published for other age- dependent biological parameters (5,6). It is interesting to note that "skin elasticity" in the above articles, measured by a semi-quantitative method but in essence measuring slackness, had the correlation coefficient 0.60 as compared with our levarometry r = 0.57. An age-dependent correlation coefficient of 0.57 is very high: in the published literature on age-dependent parameters (5) only two out of 26 correlations had higher