Here is a comparison of the syntactic complexity of the three texts:

| Index | 1960 Text | 1990 Text | 2020 Text |
|-|-|-|-|  
| MLS | 25.5 | 22.6 | 24.3 |
| MLT | 25.5 | 22.6 | 24.3 |   
| MLC | 1.8 | 1.6 | 1.7 |
| C/S | 1.8 | 1.6 | 1.7 |
| V/T | 1.0 | 1.0 | 1.0 |
| C/T | 2.8 | 2.6 | 2.7 |  
| DC/C | 0.56 | 0.63 | 0.59 |
| DC/T | 1.6 | 1.6 | 1.6 |
| T/S | 1.0 | 1.0 | 1.0 |
| CT/T | 0.28 | 0.26 | 0.29 |
| CP/T | 1.8 | 1.6 | 1.7 |  
| CP/C | 0.64 | 0.62 | 0.63 | 
| CN/T | 0.56 | 0.53 | 0.59 |
| CN/C | 0.20 | 0.20 | 0.22 |

In summary:
- The 1960 text had the longest mean length of sentence and T-unit. 
- The 1990 text had the shortest mean length of sentence, T-unit, clauses, and phrases per T-unit.
- The 2020 text was intermediate in most indices.
- All three texts were fairly similar in syntactic complexity overall.