Prior to the dissolution of the Soviet Union, estimates of Gulag victims ranged from 2.3 to 17.6 million (see a History of Gulag population estimates section). Post-1991 research by historians utilizing archival materials brought this range down considerably. According to a 1993 study of archival Soviet data, a total of 1,053,829 people died in the Gulag from 1934 to 1953. However, taking into account the fact that it was common practice to release prisoners who were either suffering from incurable diseases or near death, a combined statistics on mortality in the camps and mortality caused by the camps gives  a probable figure around 1.6 million. In her recent study, Golfo Alexopoulos made an attempt to challenge this consensus figure by encompassing those whose life was shortened due to GULAG conditions. The GULAG mortality estimated in this way yields the figure of 6 million deaths. Historian Orlando Figes and Russian writer Vadim Erlikman have posited similar estimates. Alexopoulos estimate, however, is supported by indirect and misinterpreted evidences, and has obvious methodological difficulties. The tentative historical consensus among archival researchers and historians who utilize such data is that of the 18 million people who passed through the gulag from 1930 to 1953, between 1.5 and 1.7 million perished as a result of their detention.
Question: Approximately how many years do archival researchers consider the time fram of the gulag?
Answer: 23