The development gap is widening because countries are developing at different rates. This means that a country like America is developing quickly through industry but smaller countries like places in Africa aren't developing as quickly because they have less and poorer industry. So they can't keep up with the developing countries and are left behind. This means the development gap between the countries is getting wider.
The development is widening due to different rates of development between different countries, countries like america develop quicker than countries like ghana because they have better industry and their trade involves secondary goods that sell for more, but ghana rely on trade of primary good like crops which sell for much less this can cause them to make little profit and even go into debt, widening the gap because they are unable to become as developed due to debt as richer countries like america, also they have little high quality industry.