Before the pension insurance reform, many employees had worked for many years and did not pay social insurance on their previous wages (because under the planned economy, individuals did not pay and only the employer had to pay). Therefore, there was no or lack of payment for the personal part, and then the payment was made later.

It is to use your own contributions to provide the pensions of these retired employees. As a result, the individual contributions in the book are actually missing. This missing part is called an empty account.