"Clear" as in "the overwhelming opinion of experts operating without the benefit of hindsight" or "clear" as in "a position held by the masses primarily out patriotic faith"?
The GDP charts I've seen seem to support the latter: the USSR's developing economy grew significantly faster than the US's developed economy for a sustained period of several decades. The "collapse" of the USSR didn't look so much like an adjustment (i.e. what you would expect if those numbers were completely fictitious) but rather a leveling off of growth. As for your "obvious example," 1. importing food is not necessarily indicative of a shortfall and 2. from what I understand, the central government of the USSR occasionally starved sizable chunks of its population for political reasons rather than due to actual shortfalls (e.g. while simultaneously exporting food).
From the personal experience (I was born in USSR in mid-70ies and have lived there since) 50% of the GDP should have been military expenses, including space program. Everyday life was more like to the poorest Latin America or African countries now, plus common shortage of anything but very basic food items. Even these were also often grown by people themselves. Common joke was following. Lecturer: "By 1980 Soviet Union will bypass USA economically". Student: "Better catch, but not to bypass". "Why not bypass?" Answer: "Then they would see that ass is naked".
The GDP charts I've seen seem to support the latter: the USSR's developing economy grew significantly faster than the US's developed economy for a sustained period of several decades. The "collapse" of the USSR didn't look so much like an adjustment (i.e. what you would expect if those numbers were completely fictitious) but rather a leveling off of growth. As for your "obvious example," 1. importing food is not necessarily indicative of a shortfall and 2. from what I understand, the central government of the USSR occasionally starved sizable chunks of its population for political reasons rather than due to actual shortfalls (e.g. while simultaneously exporting food).