* @return the percent as a float
	 */
	public float getUniquePercentage( short version )
	{
		int totalLen = 0;
		int uniqueLen = 0;
		if ( numVersions()==1 )
			return 0.0f;
		else
		{
			for ( int i=0;i<pairs.size();i++ )
			{
				Pair p = pairs.get( i );
				if ( p.versions.nextSetBit(version)==version )
				{
					if ( p.versions.size()==1 )
						uniqueLen+= p.length();
					totalLen += p.length();
				}
			}
			return (float)uniqueLen/(float)totalLen;
		}
	}