with switch from base pay to TDC perspective you risk one thing. As VAR COMP is volatile, the basis to which you will compare your employees(market data), will be volatile too. Business results and overall ecomnomic situation in industry might change dramatically YtY and as the data you have from market are already some months old, you risk, that with setting up your strategy on these volatile data, you will not catch up what's currently happening on the market. E.g. last year was bad, sales incentives were low, so also TDC is low. You setup your compensation approach on these data, but this year, sales are growing, so are incentives, but your increases of TDC will probably not reflect this. In my opinion it's better to set base compensation on market data separately, and keep more flexibility in VAR COMP.