Complex sentence: GDP (long stuck at its 1973 level even with a growing population) grew by about a third from early 1991 to late 1994; fixed investment, depressed since the 1981--82 crisis, more than doubled in this period.
Split into simpler sentences: GDP (long stuck at its 1973 level even with a growing population) grew by about a third from early 1991 to late 1994. Fixed investment, depressed since the 1981--82 crisis, more than doubled in this period.