Why does Shanghai's social security increase by 5% every year?

Because of the increase of average salary and payment base.

The reason why Shanghai's social security increases by 5% every year is closely related to the increase of average wages and payment base. With the development of economy and the improvement of people's living standards, the average wage level in Shanghai has increased year by year, which leads to a corresponding increase in the social security payment base, and the calculation method of the social security payment base is also linked to the average wage level.