The Statistics New Zealand figures are likely to mirror the reports from two of New Zealand's largest retailers The Warehouse Group and Briscoe Group, which both reported falls in revenue in the three months to April.
Bank of New Zealand senior economist Craig Ebert said there needed to be caution in dismissing any "truly awful" retail numbers tomorrow as being just technical data.
"To the extent this doesn't reflect contracting volumes, then it means there is some very heavy price discounting going on . . . which might well take the edge off the second quarter consumers price index [CPI]."
The other gauge of the slow-down the economy was experiencing would come from April's performance of manufacturing index (PMI) also being published tomorrow.
The last of the week's economic news would come on Friday, with the March quarter producer prices.
Mr Ebert said the BNZ expected 1.2% increases for each of the output and input prices.
That would lift their respective annual rates to 5.5% and 6.2% but the results would owe a lot to a further rise in dairy export prices, fuel, food and other raw material costs.
Stripping those out would make the core inflation story much less frightening for the Reserve Bank, Mr Ebert said.
Following the heavy job losses reported in the household labour force, calls have intensified for the central bank to slash its official cash rate from 8.25%.
Mr Ebert said wholesale money markets had already built in OCR cuts for this year and next.
However, banks were paying a big premium for their funds, and even if the Reserve Bank started cutting the cash rate next month, it would not necessarily allow retail interest rates to fall.
"The reality is that to get clear and sustained falls in New Zealand retail interest rates from here, the Reserve Bank will most probably have to cut the OCR by more than the 1.5% or so that is currently priced into the wholesale markets by mid-next year," Mr Ebert said.
Westpac and National Bank have joined the flurry of mortgage rate reductions that began on Friday.
Westpac cut its key two-year mortgage rate to 9.4% from 9.7%, matching the cut announced by ASB on Friday.
Westpac has also cut its special fighting rates of 21 months to 9.4% and 33 months to 9.29%.
National Bank cut its fixed rates across the board, also reducing its two-year rate to 9.4%.
