The article puts forward the hypothesis about the wave nature of pension systems reforms since the early 1990 under the effect of demographic and economic factors. In response to the results of previous works on this subject and statistical analysis results, wave’s mechanism has been identified. Conditions for starting the wave of pension reforms established with long-term demographic trend in periods of tension (the higher growth rates of age dependency ratio and others). The start and dynamic of the wave are determined by macroeconomic shocks arise from decreasing phase of business-cycle. The growth phase of pension reforms are followed by the period of deceleration. There is a factor that slowdowns responses to macroeconomic shocks (the decisions about pension reforms are not accepted instantly). Pension system adjusts to new conditions until further tightening. Quantitative and quality analysis of pension reforms across countries would allow to test this hypothesis. To that end an appropriate instruments have been developed: the classifier of pension reform (67 items with scoring system to estimate the depth of the changes), evaluation system for economic factors influences via sensitive to pension systems indicators and associated macroeconomic shocks. A cross-section of 24 countries generates a mix of pension reforms for the period of 1994–2019, two waves of pension reforms (1990–2008 and 2009 – present) is revealed, the hypothesis of waves nature of pension reforms is confirmed. The heart of pension systems transformations in the first way is identified. These are lowering of government pensions obligations, shifting the risks from state to population with the introduction of DCschemes. The suggestions that the implementation of second pillar is positive only for countries with well-developed financial market.  The research of second-wave of pension reforms and projection of the third way will be dealt with in the next article.