Scholars have struggled to understand the role of investment in the slow growth of post‐Independence sub‐Saharan Africa. Existing research has largely relied on national accounting data, which suggests low returns on investment in the region. This article uses data gathered during fieldwork to investigate the quality of the investment data in the national accounts of Nigeria, Africa's most populous economy. It proposes a new investment series which can be compared to those in Nigeria's national accounts for 1976–85. It provides an alternative view of investment and productivity during the country's crucial oil boom period, when Nigeria had significant funding available for investment but this investment did not result in long‐term economic growth. Data are drawn from construction surveys, publicly listed and privately held construction company financial records, and industry publications. The new series suggests that for many years of the oil boom, approximately two‐thirds of what was recorded as having been investment in Nigeria's national accounts was not investment at all. Much of this was ‘ghost construction’, projects paid for but never completed. This indicates that actual investment was far more productive than has previously been appreciated.