The author proposes a method for predicting structural changes in Polish enterprises based on Markov chain theory. This method makes it possible to analyze the entry and exit of companies in specific business sectors, as well as to examine the migration of firms across sectors. Markov chains enable forecasts of the future composition of the corporate sector as well as computations of the average remaining lifetime and average age of companies in each category based on an appropriate fundamental matrix. This can serve as the basis for further conclusions concerning not only the economy as a whole, but also its individual components. The findings presented in the article testify to the stability of Polish companies in changing economic conditions. The level of migration across sectors is low and limited to several sectors and the expected company lifetime is relatively short. On average, the lifetime of Polish companies is less than half that of Belgian companies surveyed by the National Bank of Belgium, for example. Generally, Nehrebecka says, transport companies have the shortest lifetimes in Poland, followed by companies active in sectors such as construction, “other services” and trade. On the other hand, companies operating in agriculture, the hunting-and-forestry sector and industry tend to stay the longest on the market. The average maturity of a sector, measured with the so-called “closeness to extinction” index for all the companies, is 46%. Non-specialized exporters show the highest average age in the analyzed sectors. State-owned companies have significantly higher average age and remaining lifetime than private companies. The larger the company, the higher is its average age and average remaining lifetime. According to Nehrebecka, studies of the demographic evolution of businesses may be an additional point of reference for the evaluation of monetary policy transmission mechanisms and for shaping the institutional and legal environments in which businesses operate.