Figure 3a shows the visible trade data in United States dollars (USD) in billions for Mexico in 2018 and 2019.
| 2018 | 2019 | |
|---|---|---|
| Visible imports USD (billions) | 312 | 298 |
| Visible exports USD (billions) | 305 | 301 |
Calculate the balance of trade for Mexico in 2018 and 2019.