Source of the claims: the Wall Street Journal's Pulitzer Prize-winning columnist Bret Stephens (Nov. 2016).

Both claims are correct only when gross domestic product is measured in "current U.S. dollars," meaning it is calculated at market exchange rates for national currencies without adjusting either for inflation or for variations in the cost of living. Other ways to measure GDP include using "constant prices," which have been adjusted for inflation, and/or purchasing power parity (PPP) exchange rates, which are adjusted for differences in the cost of goods and services in each country. According to the CIA's World Factbook, “market exchange rates are frequently established by a relatively small set of goods and services (the ones the country trades) and may not capture the value of the larger set of goods the country produces… The data derived from the PPP method probably provide the best available starting point for comparisons of economic strength and well-being between countries.”

In short, when tested by any of the World Bank's measures of GDP other than current U.S. dollars, the claims do not hold up and Russia's economic picture looks much rosier:

Claim 1: Russia’s GDP contracted by 40% between 2013 and 2015.

Source: World Bank

Claim 2: Russia's economy is now half the size of Great Britain’s.

Again, the numbers depend on the way of calculating GDP. If measured in terms of PPP and adjusted for inflation, Russia's economy in 2015 was actually larger than Britain's. Final data for 2016 were not available as of this writing, but given estimates that Russia's economy will shrink by 0.6%, while Britain's will grow by 2%, the numbers should not be wildly different from 2015's.

Source: World Bank