The Economist piece is just a summary of Dimson, Marsh, and Staunton (2013).

It does? From the Economist piece, fourth paragraph:

Within a couple of years, however, investors in Russian equities and in government bonds and bills had all been wiped out.

And if you had bothered to C-f in the PDF, they certainly did take it into account:

When incorporating these countries into our world index, we assume that shareholders and domestic bondholders in Russia and China suffered total losses in 1917 and 1949, respectively. We then re-include these countries in the index when their markets re-opened in the early 1990s.

...Last year’s 2012 Yearbook reported an annualized real return on the world bond index of 1.75%. Figure 9 shows that with the inclusion of Austria, plus Russia and China, where we assume domestic bond investors lost everything in 1917 and 1949, the annualized return falls by 0.05% to 1.70%.

At first sight, this seems a remarkably small reduction. Closer scrutiny shows that the losses on Russian bonds in 1917 and Chinese bonds in 1949 reduced the annualized return on the world bond index by 0.10% and 0.12%, respectively. However, in other years, bond returns for these countries were slightly higher than for the remaining countries in the index, so the net impact over 113 years was very modest. After 2012 updates plus revised bond series for several countries, the 2013 Yearbook now records an annualized real return on the world bond index of 1.75%, unchanged from 2012.

Amusingly, neither equity nor bond holdings may've suffered a total loss in Russia or China:

Shareholders in firms with substantial overseas assets may have salvaged some equity value, e.g. Chinese stocks with assets in Hong Kong and Formosa/Taiwan. Similarly, Russian and Chinese bonds held overseas continued to be traded in London, Paris and New York long after 1917 and 1949. While no interest was paid, the Russian and Chinese governments eventually – in the 1980s and 1990s – paid compensation to some countries, but overseas bondholders still suffered a 99% loss of present value.