In June 1951, the JPBL issued a rule granting to each team the exclusive right to negotiate future contracts with players already under contract.
Three factors prompted the change in rules.(9) First, North American MLB introduced a player draft in 1965, a development which the JPBL closely monitored.
Since then, the JPBL has held one annual draft in mid-November,(10) A player cannot be drafted until he graduates from high school.
The lower level of signings in the 1960s and early 1970s may have been due to JPBL controls on signing bonuses paid to new recruits.
This is because JPBL teams have not developed the extensive layers of minor league teams observed in North American MLB.
JPBL draft rules are somewhat complicated and have changed twice since 1965.
The JPBL limits each team to two foreign players on its major league roster and one foreign player on its minor league roster.(14) There is open bidding for new foreign players, and the player is bound by the JPBL reserve clause for veterans after signing.(15) The open market for foreign players implies, once again, that the highest quality foreign talent will sign with the teams which most value winning and those teams will have a competitive edge.
In this section we conduct a variety of empirical tests to determine whether the switch to the draft in 1965 improved various measures of competitive balance among JPBL teams.
Empirical analysis using JPBL data provides some evidence that changes in the rules for assigning property rights to new baseball players increased competitive balance over time in both leagues under the player draft regime.
Our results for the JPBL are virtually identical to Fort and Quirk's  results for North American MLB.
In our case, using JPBL data is preferable, as the change in the JPBL regime for allocating new players comes close to being a "natural experiment" against the background of an relatively stable institutional environment.