The space available for making bids. The cheaper the bid, the less bidding space it uses.
The first example shows highly economical use of bidding space. The second example, with the jump overcall and less convenient suit ranks, is far less economical. In constructive bidding, it is usually preferable to conserve bidding space (at least until a fit is found) in order to exchange the maximum amount of information. Conversely, it is often in the interest of the players with weaker hands to restrict the amount of space available to their opponents, for instance by making pre-emptive bids.