| Year | Pieces of Mail |
| 1954 | 43,500,000 |
| 1956 | 58,200,000 |
| 1958 | 65,400,000 |
| 1960 | 108,000,000 |
| 1962 | 110,100,000 |
| 1964 | 110,500,000 |
| 1966 | 197,500,000 |
| 1968 | 178,200,000 |
| 1970 | 201,000,000 |
| 1972 | 308,900,000 |
| 1974 | 321,000,000 |
| 1976 | 401,100,000 |
| 1978 | 430,200,000 |
| 1980 | 511,300,000 |
| 1982 | 581,700,000 |
| 1984 | 924,600,000 |
| 1986 | 758,700,000 |
| 1988 | 804,900,000 |
| 1990 | 564,200,000 |
| 1992 | 458,000,000 |