Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| School | City | Mascot | County | Year joined | Previous Conference | Year Left | Conference Joined |
| --- | --- | --- | --- | --- | --- | --- | --- |
| East Chicago Roosevelt | East Chicago | Roughriders | 45 Lake | 1963.0 | Northern Indiana | 1968.0 | Indiana Lake Shore |
| East Chicago Washington | East Chicago | Senators | 45 Lake | 1963.0 | Northern Indiana | 1968.0 | Indiana Lake Shore |
| Gary Emerson | Gary | Tornado | 45 Lake | 1963.0 | Northern Indiana | 1981.0 | none (school closed, reopened as Emerson VPA) |
| Gary Froebel | Gary | Blue Devils | 45 Lake | 1963.0 | Northern Indiana | 1969.0 | none (school became MS, closed 1977) |
| Gary Mann | Gary | Horsemen | 45 Lake | 1963.0 | Northern Indiana | 2004.0 | none (school closed) |
| Gary Tolleston | Gary | Blue Raiders | 45 Lake | 1963.0 | Northern Indiana | 1969.0 | none (school became MS, closed 2007) |
| Hammond | Hammond | Wildcats | 45 Lake | 1963.0 | Northern Indiana | 1968.0 | Indiana Lake Shore |
| Hammond Clark | Hammond | Pioneers | 45 Lake | 1963.0 | Northern Indiana | 1968.0 | Indiana Lake Shore |
| Hammond Tech | Hammond | Tigers | 45 Lake | 1963.0 | Northern Indiana | 1968.0 | Indiana Lake Shore |
| Valparaiso | Valparaiso | Vikings | 64 Porter | 1963.0 | Northern Indiana | 1968.0 | Independents |
| Whiting | Whiting | Oilers | 45 Lake | 1963.0 | Northern Indiana | 1968.0 | Indiana Lake Shore |
| Hammond Gavit | Hammond | Gladiators | 45 Lake | 1966.0 | Independents | 1968.0 | Indiana Lake Shore |
| Hammond Morton | Hammond | Governors | 45 Lake | 1966.0 | Independents | 1968.0 | Indiana Lake Shore |
| Hobart | Hobart | Brickies | 45 Lake | 1966.0 | Independents | 1968.0 | Independents |
| Andrean | Gary | 59ers | 45 Lake | 1968.0 | Independents | 1975.0 | Independents (school moved to Merrillville ) |
| Gary Wirt | Gary | Troopers | 45 Lake | 1970.0 | Calumet | 2009.0 | school closed |
Question:
What is the year that the Roughriders left the conference?
Answer:
1968.0