Bankroll Requirements over Several Tables

[Sciolist]

Something I'm not certain on is bankroll requirements when playing several tables. How does this affect it? I have heard arguments for every stance - reducing, increasing, no effect.

By increasing the number of tables, obviously you have more in play (more relevant to NL I suppose), but your variance isn't neccessarily increased. How does the mathematics of this work? What kind of bankroll should I consider whilst playing 3x $200 NL tables? How about for 4x 1/2 Limit tables?

Any advice welcome.