The phrase "has been flat over" is correct and usable in written English.
You can use it to describe an activity or trend that has not changed or fluctuated in some time period. For example, "Sales of luxury cars have been flat over the last six months."
Despite the Fed's steady march toward more accommodation, the trade-weighted dollar has been flat over the past six months.
The index has been erratic this year, rising one month and falling the next, but has been flat over all.
"Spending has been flat over the past six months," said Maryse Pogodzinski, an economist at JPMorgan Chase in Paris.
As one indicator of that risk, Shell's stock price has been flat over the past year while that of Chevron, which is more oil-based, has risen about 15 percent.
Home student demand for postgraduate study has been flat over recent years, with provision effectively sustained by strong international demand – there are as many Chinese taught postgraduates in the UK as their domestic counterparts.
As for business, investment spending — everything from computer equipment to research and development to warehouses — has been flat over the past year and has not grown materially from pre-recession levels, according to Mark M. Zandi, chief economist of Moody's Analytics.
Prices have been flat over the past year, and tight lending restrictions continue to suppress the market, he said.
The E.P.I. report shows that the real wages of college-educated workers have been flat over the last decade as well, though workers with advanced degrees have done better.
The second half is likely to have been strong; the broker is forecasting a moderation in the decline in sales, with revenues expected to have been flat over the fourth quarter.
Growth, much like Wheat Thins themselves, had been flat over the last few years, but the brand has had month-over-month increases in both revenue and market share for each of the last six months, according to Symphony/IRI Group, whose data does not include Wal-Mart.
Until the recent crisis, the last time bond yields were that low was in 1950; over the subsequent 30 years, bonds lost seven-eighths of their value in real (after inflation) terms.As yet, however, there is no sign of inflation; American prices have been flat over the past 12 months.
