Tax Buoyancy

Tax buoyancy measures how responsive tax revenue is to growth in the tax base. It is commonly expressed as the ratio of the percentage change in tax revenue to the percentage change in nominal GDP or GSDP, used as a broad proxy for the tax base.

Measurement and interpretation

The standard expression is: tax buoyancy = percentage change in tax revenue divided by percentage change in the tax base. For example, if tax revenue rises by 12 percent while nominal GDP rises by 10 percent, buoyancy is 1.2.

• A buoyancy of more than 1 means tax revenue is growing faster than the tax base.
• A buoyancy of 1 means tax revenue and the tax base are growing proportionately.
• A buoyancy of less than 1 means revenue is failing to keep pace with growth in the tax base.

What buoyancy captures

Tax buoyancy reflects both the economy's automatic revenue response and the effects of discretionary tax changes. It may be influenced by tax rates, exemptions, economic composition, inflation, compliance, formalisation and tax administration.

• A high value may indicate an expanding effective tax base, better compliance, progressive taxation or tax increases.
• A low value may indicate exemptions, weak compliance, growth concentrated in lightly taxed activities or tax reductions.
• Buoyancy shows the pace of revenue mobilisation, but by itself does not identify which factor caused it.

Difference from tax elasticity

Tax elasticity measures the automatic response of revenue to the tax base after excluding the effects of discretionary policy changes. Buoyancy includes such changes, so it is the broader measure of the observed revenue response.

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