_15_ _Results_ Table 6. Ratio of deaths from circulatory system diseases<sup>to</sup> deaths from Infectious and parasitic diseases, by region, 19702015

|_Region_|_1970_|_1985_|2000|_2015_|
|---|---|---|---|---|
|World|0.69<br>|0.89<br>|1.62<br>|2.39<br>|
|Developed countries|3.98|5.73<br>|7.52<br>|7.69<br>|
|Developing countries|0.40|0.52<br>|1.12<br>|1.82<br>|
|Industrial market|5.63|6.64<br>|9.61<br>|11.88<br>|
|Induswtrial<br>nonmarket|2.44<br>|4.72<br>|5.24<br>|4.41<br>|
|Latin America and Caribbean|0.68|1.09|2.46|4.74<br>|
|Sub-Saharan Africa|0.23|0.27|0.38<br>|0.54<br>|
|Middle East and North Africa|0.37|0.41<br>|0.81<br>|1.26<br>|
|Asia|0.42|0.60<br>|1.55<br>|2.75<br>|
|India|0.40<br>|0.29<br>|1.01<br>|1.64<br>|
|China|0.53<br>|1.19<br>|3.52<br>|8.37<br>|
|Other Asia|0.32|0.56|1.04|1.69|

in proportion for the last two of these causes.

The projections of mortality by cause are not straightforward extrapolations<sup>from</sup> past experience, but involve a combination of population<sup>projections with predictive</sup> equations for mortality rates by cause. An alternative, much<sup>simpler, procedure would</sup> have been to take the change in percentage of deaths due<sup>to a given cause from 1970</sup> to 1985 and extrapolate this linearly into the future. This<sup>alternative procedure would</sup> have given quite different results: for the world as a whole<sup>by 2000, a larger share of</sup> deaths due to infectious and parasitic diseases (24<sup>instead of 21 percent), a</sup> correspondingly lower share due to circulatory system<sup>diseases (29 instead of 35</sup> percent), and smaller variations for the other causes. For specific<sup>regions, the differences</sup> would have been greater: for the Middle East and North Africa<sup>by 2015, for instance,</sup> a linear extrapolation would give 39 percent of deaths due<sup>to infectious and parasitic</sup> diseases, whereas the regression-based procedures give<sup>only 23 percent.</sup> Some insight into why the calculations come out as they do<sup>can be obtained by</sup> decomposing future changes in the distribution of deaths.<sup>Such changes maybe related</sup> to changes in the age-sex structure of the population, changes<sup>in mortality levels from</sup> all causes within age-sex groups, or changes in the distribution<sup>of deaths by cause</sup> within age-sex groups. Projections with fixed mortality or<sup>fixed distributions of deaths</sup> by cause can help distinguish these components of change,<sup>if one accepts the necessary</sup> assumptions: for instance, that mortality can change without<sup>a simultaneous change in</sup> the distribution of deaths by cause, or, in other words,<sup>that a similar proportional</sup> change in deaths across causes is conceivable. Table 7<sup>shows, first, the percentage of</sup> deaths due to each cause in 1985; second, the projected increase<sup>or decrease in this</sup> percentage (by 2000 and 2015) due to contemplated changes<sup>in the age-sex structure,</sup> assuming fixed mortality; third, the further projected increase<sup>or decrease in this</sup> percentage if mortality is allowed to decline but the distibution<sup>of deaths by cause is</sup> fixed within age-sex groups; and fourth, the further projected<sup>increase or decrease due</sup> to changes in the distribution of deaths by cause within<sup>age-sex groups. Totaling the</sup> components for 2000 for any given cause and adding the<sup>1985 figure gives the projected</sup> percentage of deaths due to that cause by 2000.