and Summary of Main Points -- 1. General Framework -- 1.1 Three schools -- 1.2 Cycles or fluctuations ? -- 1.3 Socialism -- 1.4 Statistical definition of investments -- 1.5 Theory and statistical reality -- 1.6 The relevance of cycle models -- 1.7 Formalised summary -- 2. Three Schools of Thought -- 2.1 Control theory models -- 2.2 Endogenous models -- 2.3 Common elements -- 2.4 Exogenous models -- 3. Measurement of Investment Fluctuations -- 3.1 Distortion of GINV data -- 3.2 Traps of time series analysis -- 3.3 East-West comparison of GINV fluctuations -- 3.4 Synchronization of investment fluctuations -- 4. Common Patterns and Particularities - A Historical Analysis -- 4.1 The method -- 4.2 Construction output -- 4.3 Industrial output -- 4.4 Imports -- 4.5 Standard of living -- 4.6 Domestic utilization of NMP -- 4.7 Role of the harvest and foreign credits -- 5. Closing Remarks on Measurement and Control -- 5.1 The measurement trap -- 5.2 The definition trap -- 5.3 Micro-economic conditions of measurement -- Appendix I: Two Hungarian Case Studies -- 1. The impact of investment fluctuations on the labour market -- 2. Maintenance - capital repair - investment -- 3. Conclusions -- Appendix II: Basic Data.