> that lump sum back pay may put them in a situation where they actually get paid pay less.

You're beginning to mix apples with oranges. In RR contract negotiations, "lump sum" refers to a specific dollar amount of money which is paid equally to each employee if the contract is ratified. "Back-pay" is the difference between what you earned while working under the expired contract and what your earnings would have been had a new contract been agreed to before the previous one expired. Lump sums almost always amount to far less than what an employee would have earned if a new contract had become effective at the moment the old one expired. Thus, offering them has become a monetary incentive for management to stall negotiations as long as possible in hopes we will lose patience and give in.

When I was working for Atk, we went for 10 years "without a contract" because Atk's vp-labor relations of the time simply refused to come to negotiating table, wouldn't even set foot in the room. Then when he finally did agree to a contract proposal, it offered us a $5,000 lump sum payment to make up for the loss of earnings. We voted it down, the negotiations went to a PEB, and the PEB recommended "full back-pay". As a result of the PEB's recommendations, which we quickly voted in, some of us received more back pay than others. My back-pay was at least 10 times that lump sum payment, so please tell me how I could receive less.