The story of evolution of Bank Zachodni SA (BZ SA) and Wielkopolski Bank Kredytowy SA (WBK SA) in 1989-1999 is an example of a "live laboratory" which may be analysed to assess the impact of privatisation on the efficiency of commercial banks.

The unique research value of this case is that after a period of state ownership of BZ SA and WBK SA (1989-1993), i.e. directly after the establishment of nine commercial banks on the basis of the National Bank of Poland (the so-called Group of Nine), the banks evolved in different directions and at a different pace. In 1993 WBK SA was the first bank of the Group of Nine to be privatised by a public offering of the company's shares on the Warsaw Stock Exchange. BZ SA remained a state-owned bank until 1999, where it was privatised by selling the majority stake to a strategic investor, Allied Irish Bank (AIB). Finally, in 2001 AIB, being the major shareholder in both banks, commenced the merger of the two banks and established the sixth largest bank in Poland as regards the volume of assets.

The multi-layer analysis of BZ SA and WBK SA in the years 1989-1999 shows that the banks' evolution in the said period featured the following characteristics:

• similar situation at the beginning of operation in 1989,
• similar development of both banks when owned by the state in the years 1989-1993, (more specifically, up to the entry to WBK SA of a strategic investor),
• growing diversity between BZ SA and WBK SA in 1994-1999 (as regards development, efficiency and security indicators), i.e. in the period when BZ SA was still a state-owned bank, and WBK SA had already been privatised,
• decreased efficiency and security indicators of BZ SA between their levels in 1993 and 1999.

The analysis of the developments in BZ SA and WBK SA in the years 1989-1999 confirms the results of works and research surveys on the influence of ownership on the efficiency of banking institutions, presented in the first part of the article. It shows that private ownership in the banking sector is conducive to relieving the banking sector of political influence, to improved management quality, raised financial and operating efficiency and to the introduction of efficient risk management strategies (especially as regards lending). Thus, private capital in the banking sector is rated more efficient than state-owned capital.